Difference between revisions of "User:Tohline/ThreeDimensionalConfigurations/RiemannStype"

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==Equilibrium Conditions for Riemann S-type Ellipsoids==
==Equilibrium Conditions for Riemann S-type Ellipsoids==
We begin this section by quoting from the first paragraph in &sect;II, p. 892 of [https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)]. "<font color="darkgreen">The problem that is to be considered &hellip; is that of a homogeneous mass, rotating uniformly with an angular velocity <math>\vec\Omega_f</math>, with internal motions having a uniform vorticity <math>~\vec\zeta</math> in the direction of <math>~\Omega_f</math> and in the frame of reference rotating with the angular velocity <math>~\vec\Omega_f</math>.</font>"  As did Chandrasekhar, we will find it useful to refer to the ratio of these highlighted frequencies as the key model parameter,
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~f</math>
  </td>
  <td align="center">
<math>~\equiv</math>
  </td>
  <td align="left">
<math>~\frac{\zeta}{\Omega_f} \, .</math>
  </td>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)], p. 892, &sect;II, Eq. (15)
</div>
===Based on Virial Equilibrium===


Pulling from Chapter 7 &#8212; specifically, &sect;48 &#8212; of [[User:Tohline/Appendix/References#EFE|Chandrasekhar's EFE]], we understand that the semi-axis ratios, <math>~(\tfrac{b}{a}, \tfrac{c}{a})</math> associated with Riemann S-type ellipsoids are given by the roots of the equation,
Pulling from Chapter 7 &#8212; specifically, &sect;48 &#8212; of [[User:Tohline/Appendix/References#EFE|Chandrasekhar's EFE]], we understand that the semi-axis ratios, <math>~(\tfrac{b}{a}, \tfrac{c}{a})</math> associated with Riemann S-type ellipsoids are given by the roots of the equation,
Line 162: Line 184:
</table>
</table>
</div>
</div>
where,
<span id="A12B12">where,</span>
<div align="center">
<div align="center">
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">
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</table>
</table>


As an aid in determining both values of the parameter, <math>~f</math>, we note as well that,
<table border="0" cellpadding="5" align="center">


<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <td align="center" colspan="10"><b>TEST (part 2)</b></td>
  <td align="right">
<math>~f_+ \cdot f_-</math>
  </td>
   <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\frac{1}{\alpha} = \biggl[ \frac{a^2 + b^2}{ab}\biggr]^2 \, .
</math>
  </td>
</tr>
</tr>
<tr>
</table>
 
 
<div align="center" id="TestPart2">
<table border="1" align="center" cellpadding="8">
<tr>
  <td align="center" colspan="10"><b>TEST (part 2)</b></td>
</tr>
<tr>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
   <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
   <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
Line 299: Line 340:
</tr>
</tr>
</table>
</table>
</div>


===Based on Detailed Force Balance===
====The Steady-State Condition====


Now, according to [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)], at any coordinate position inside or on the surface of the ellipsoid, <math>~(x, y)</math>, the three components of the velocity as viewed from a frame of rotation that is spinning at the equilibrium configuration's frequency, <math>~\Omega</math>, are,
As has been pointed out in our [[User:Tohline/PGE/RotatingFrame#Euler_Equation_.28rotating_frame.29|introductory discussion of the Principal Governing Equations]], quite generally we can write the
 
<div align="center">
<font color="#770000">'''Eulerian Representation'''</font><br />
of the Euler Equation <br />
<font color="#770000">'''as viewed from a Rotating Reference Frame'''</font>
 
<math>\biggl[\frac{\partial\vec{v}}{\partial t}\biggr]_\mathrm{rot} + ({\vec{v}}_\mathrm{rot}\cdot \nabla) {\vec{v}}_\mathrm{rot}= - \frac{1}{\rho} \nabla P - \nabla \biggl[\Phi_\mathrm{grav} - \frac{1}{2}|{\vec{\Omega}}_f \times \vec{x}|^2 \biggr] - 2{\vec{\Omega}}_f \times {\vec{v}}_\mathrm{rot} \, ,</math>
</div>
 
where, <math>~{\vec{\Omega}}_f </math> specifies the time-invariant rotation frequency of the frame and the orientation of the vector about which the frame spins. The condition for detailed force balance in a steady-state configuration is obtained by setting <math>~[\partial \vec{v}/\partial t]_\mathrm{rot} = 0</math>.  If we furthermore make the substitution, <math>~\nabla H = \nabla P/\rho</math>, where <math>~H</math> is enthalpy &#8212; an equation of state relation that is appropriate for a [[User:Tohline/SR#Barotropic_Structure|barytropic system]] &#8212; we obtain,
<div align="center">
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\vec{v}</math>
<math>~({\vec{v}}_\mathrm{rot} \cdot \nabla ){\vec{v}}_\mathrm{rot}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 312: Line 367:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\lambda \biggl( \frac{ay}{b} , - \frac{bx}{a} , 0 \biggr) \, ,</math>
<math>~
- \nabla\biggl[ H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)\biggr] - 2{\vec{\Omega}}_f \times {\vec{v}}_\mathrm{rot} \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>


where, <math>~\lambda</math> is an overall scale factor.  But, according to &sect;48 of EFE, we see that,
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (4)
</div>
====Adopted Velocity Flow-Field====
 
As [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)] has pointed out [text that is taken directly from that publication appears here in an orange-colored font], <font color="orange">the velocity field of a Riemann S-type ellipsoid as viewed from a frame rotating with angular velocity <math>~{\vec{\Omega}}_f = \boldsymbol{\hat{k}} \Omega_f</math> takes the following form:</font>
<div align="center">
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\vec{u}</math>
<math>~{\vec{v}}_\mathrm{rot}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
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   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\biggl( Q_1 y , Q_2 x , 0 \biggr) \, ,</math>
<math>~\lambda \biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \biggl(\frac{b}{a}\biggr)x \biggr\, ,</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
where,
 
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (3)
</div>
 
 
<font color="orange">where <math>~\lambda</math> is a constant that determines the magnitude of the internal motion of the fluid, and the origin of the x-y coordinate system is at the center of the ellipsoid.  This velocity field <math>~{\vec{v}}_\mathrm{rot}</math> is designed so that velocity vectors everywhere are always aligned with elliptical stream lines by demanding that they be tangent to the</font> equi-''effective''-potential <font color="orange"> contours, which are concentric ellipses.</font>
 
<table border="1" align="center" cellpadding="10" width="65%"><tr><td align="left">
Plugging Ou's expression for  <math>~{\vec{v}}_\mathrm{rot}</math> into the expression on the left-hand side of the steady-state Euler equation, we see that for Riemann S-type ellipsoids,
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~Q_1</math>
<math>~({\vec{v}}_\mathrm{rot} \cdot \nabla){\vec{v}}_\mathrm{rot}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~\equiv</math>
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>
<math>~
  </td>
\biggl[ \lambda\biggl(\frac{a}{b}\biggr)y \frac{\partial}{\partial x} - \lambda\biggl(\frac{b}{a}\biggr)x \frac{\partial}{\partial y} \biggr]
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp; </td>
\biggl[\boldsymbol{\hat{\imath}}\lambda\biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \lambda\biggl( \frac{b}{a}\biggr)x \biggr]</math>
  <td align="right">
<math>~Q_2</math>
  </td>
  <td align="center">
<math>~\equiv</math>
  </td>
  <td align="left">
<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta \, ,</math>
   </td>
   </td>
</tr>
</tr>
</table>
and  <math>~\zeta</math> is the scalar magnitude of the vorticity vector, <math>~\vec\zeta</math>.  The transformation from EFE's notation to the one used by Ou is, then,
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\lambda \biggl( \frac{a}{b} \biggr) </math>
&nbsp;
   </td>
   </td>
   <td align="center">
   <td align="center">
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   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>
<math>~
- \boldsymbol{\hat{\jmath}} \biggl[ \lambda\biggl(\frac{a}{b}\biggr)y\biggr] \frac{\partial}{\partial x} 
\biggl[ \lambda\biggl( \frac{b}{a}\biggr)x \biggr]
- \boldsymbol{\hat{\imath}}
\biggl[ \lambda\biggl(\frac{b}{a}\biggr)x\biggr] \frac{\partial}{\partial y} 
\biggl[\lambda\biggl(\frac{a}{b}\biggr)y \biggr]
</math>
   </td>
   </td>
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp; </td>
</tr>
 
<tr>
   <td align="right">
   <td align="right">
<math>~- \lambda \biggl( \frac{b}{a} \biggr) </math>
&nbsp;
   </td>
   </td>
   <td align="center">
   <td align="center">
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   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta </math>
<math>~
-\lambda^2\biggl[ \boldsymbol{\hat{\imath}} x + \boldsymbol{\hat{\jmath}} y \biggr]
=
-\nabla\biggl[\frac{1}{2}\lambda^2(x^2 + y^2\biggr] \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
<table border="0" cellpadding="5" align="center">


<tr>
 
----
 
Alternatively, from a [[User:Tohline/PGE/Euler#in_terms_of_the_vorticity:|separate discussion of vector identities]] we realize that,
<div align="center">
<math>
(\vec{v}\cdot\nabla)\vec{v} = \frac{1}{2}\nabla(\vec{v}\cdot \vec{v}) + \vec{\zeta}\times \vec{v} ,
</math>
</div>
where, <math>\vec\zeta \equiv \nabla\times\vec{v}</math> is the fluid vorticity.  Plugging in Ou's expression for <math>~{\vec{v}}_\mathrm{rot}</math>, we find that &hellip;
<table border="0" cellpadding="5" align="center">
 
<tr>
   <td align="right">
   <td align="right">
<math>~\Rightarrow ~~~ \lambda </math>
<math>~\vec{\zeta} = \nabla\times {\vec{v}}_\mathrm{rot}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~-\boldsymbol{\hat{k}} \lambda \biggl[ \frac{b}{a} + \frac{a}{b} \biggr] \, ;</math>
  </td>
</tr>
<tr><td align="center" colspan="3">
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 551, &sect;2, Eq. (17)
</td></tr>
<tr>
  <td align="right">
<math>~\vec{\zeta} \times {\vec{v}}_\mathrm{rot}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~-\lambda^2\biggl[\boldsymbol{\hat{\jmath}} \biggl(1 + \frac{a^2}{b^2}\biggr)y + \boldsymbol{\hat{\imath}} \biggl(1 + \frac{b^2}{a^2}\biggr)x \biggr] \, ; </math> &nbsp; &nbsp; and,
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\frac{1}{2}\nabla( {\vec{v}}_\mathrm{rot} \cdot  {\vec{v}}_\mathrm{rot} )</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 392: Line 500:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~- \biggl[ \frac{a b}{a^2 + b^2} \biggr]\zeta = - \biggl[ \frac{b}{a} + \frac{a}{b} \biggr]^{-1} \zeta\, ,</math>
<math>~\lambda^2\biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{b}{a}\biggr)^2x + \boldsymbol{\hat{\jmath}} \biggl(\frac{a}{b}\biggr)^2y  \biggr] \, .</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
which, gratifyingly agrees with Ou's equation (17).


==Models Examined by Ou (2006)==
Hence, we again appreciate that, for Riemann S-type ellipsoids,
<table border="0" cellpadding="5" align="center">


===His Tabulated Model Parameters===
<tr>
Table 1 (see below) lists a subset of the Riemann S-type ellipsoids that were studied by [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)]; properties of various so-called ''Direct'' configurations can be found in Ou's Table 1, while properties of various ''Adjoint'' configurations can be found in his Table 5.  Each row of ''our'' Table 1 was constructed as follows:
   <td align="right">
<ul>
<math>~( {\vec{v}}_\mathrm{rot} \cdot \nabla){\vec{v}}_\mathrm{rot} </math>
  <li>The pair of axis ratios <math>~(\tfrac{b}{a}, \tfrac{c}{a} )</math> associated with one of Ou's (2006) uniform-density, incompressible <math>~(n=0)</math> ellipsoid models (columns 1 and 2 from Ou's Table 1) has been copied into columns 1 and 2 of ''our'' table.</li>
  <li>Properties of ''Direct Configurations'' &hellip;</li>
  <ul>
    <li>The pair of parameter values <math>~(\omega_\mathrm{analytic}, \lambda_\mathrm{analytic})</math> that is required in order for this to be an <b>equilibrium</b> configuration &#8212; as specified by the above set of analytical expressions from EFE &#8212; is copied from, respectively, columns 11 and 13 of Ou's Table 1 into columns 3 and 4 of ''our'' table; in our table, the "analytic" subscript has been dropped from the column headings.</li>
    <li>The value of the equilibrium configuration's vorticity, <math>~\zeta</math> &#8212; see column 5 of our table &#8212; has been determined from the expression,<br /><table border="0" align="center"><tr><td align="center"><math>~\zeta = - \biggl[ \frac{1 + (b/a)^2}{b/a} \biggr] \lambda \, .</math></td></tr></table></li>
    <li>Column 6 of our table lists the value of the frequency ratio, <math>~f \equiv \zeta/\omega</math>.
   </ul>
  <li>Properties of ''Adjoint Configurations'' [in order to distinguish from ''Direct'' configuration properties, a superscript &dagger; has been attached to each parameter name] &hellip;</li>
  <ul>
    <li>As listed in column 7 of our Table, the "spin" angular velocity of the ''adjoint'' equilibrium configuration has been determined from the vorticity of the ''direct'' configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~\omega^\dagger = \zeta \biggl[\frac{b/a}{1 + (b/a)^2}\biggr] \, .</math></td></tr></table></li>
    <li>As listed in column 10 of our Table, the ratio <math>~(f^\dagger)</math> of the vorticity to the angular velocity in the ''adjoint'' equilibrium configuration has been determined from the same ratio <math>~(f)</math> in the ''direct'' configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~f^\dagger = \frac{1}{f} \biggl\{ \frac{[1 + (b/a)^2]^2}{(b/a)^2} \biggr\} \, .</math></td></tr></table></li>
  <li>As indicated, the value of the vorticity in the ''adjoint'' equilibrium configuration (column 9 of our table) has been determined from a product of <math>~\omega^\dagger</math> and <math>~f^\dagger</math>.</li>
    <li>As listed in column 8 of our table, the value of the parameter, <math>~\lambda^\dagger</math>, has been determined from the vorticity in the ''adjoint'' equilibrium configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~\lambda^\dagger = -~ \zeta^\dagger \biggl[ \frac{b}{a} + \frac{a}{b}\biggr]^{-1} \, .</math></td></tr></table></li>
  </ul>
</ul>
 
<table border="1" align="center" cellpadding="8" width="90%">
<tr>
  <td align="center" colspan="10">
<b>Table 1: &nbsp; Example Riemann S-type Ellipsoids</b><br />
[Cells with a pink background contain numbers copied directly from Table 1 of [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)]]<br />
[Cells with a yellow background contain numbers drawn from Table IV (p. 103) of EFE]
   </td>
   </td>
</tr>
   <td align="center">
<tr>
<math>~=</math>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
  <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
  <td align="center" rowspan="1" colspan="4">
Properties of<br /><b>''Direct'' Configurations</b>
   </td>
   </td>
   <td align="center" rowspan="1" colspan="4">
   <td align="left">
Properties of<br /><b>''Adjoint'' Configurations</b>
<math>~-\lambda^2\biggl[ \boldsymbol{\hat{\imath}} x + \boldsymbol{\hat{\jmath}} y \biggr] </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~-\nabla\biggl[\frac{1}{2}\lambda^2(x^2 + y^2)  \biggr] \, .</math>
   </td>
   </td>
</tr>
</tr>
</table>
</td></tr></table>
The steady-state Euler-equation specification therefore becomes,
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" rowspan="1"><math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math></td>
   <td align="right">
   <td align="center" rowspan="1"><math>~\lambda</math></td>
<math>~-\nabla\biggl[\frac{1}{2} \lambda^2(x^2 + y^2)  \biggr]</math>
   <td align="center" rowspan="1"><math>~\zeta </math></td>
  </td>
   <td align="center" rowspan="1"><math>~f \equiv \frac{\zeta}{\omega}</math></td>
   <td align="center">
  <td align="center" rowspan="1"><math>~\omega^\dagger </math></td>
<math>~=</math>
  <td align="center" rowspan="1"><math>~\lambda^\dagger </math></td>
   </td>
  <td align="center" rowspan="1"><math>~\zeta^\dagger = \omega^\dagger f^\dagger</math></td>
   <td align="left">
   <td align="center" rowspan="1"><math>~f^\dagger </math></td>
<math>~
- \nabla\biggl[ H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)\biggr] - \nabla\biggl[\Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr)  \biggr] \, .
</math>
   </td>
</tr>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (5)
</div>
<font color="orange">Hence, within the configuration the following Bernoulli's function must be uniform in space:</font>
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center">(1)</td>
   <td align="right">
  <td align="center">(2)</td>
<math>~
  <td align="center">(3)</td>
H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)  
   <td align="center">(4)</td>
- \frac{1}{2} \lambda^2(x^2 + y^2)
   <td align="center">(5)</td>
+ \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr)
  <td align="center">(6)</td>
</math>
   <td align="center">(7)</td>
   </td>
   <td align="center">(8)</td>
   <td align="center">
  <td align="center">(9)</td>
<math>~=</math>
   <td align="center">(10)</td>
   </td>
   <td align="left">
<math>~
C_B \, ,
</math>
   </td>
</tr>
</tr>
<tr>
</table>
  <td align="center" rowspan="7" bgcolor="white">0.90</td>
 
  <td align="center" bgcolor="pink">0.795</td>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (6)
  <td align="center" bgcolor="pink">1.14704</td>
</div>
  <td align="center" bgcolor="pink">0.43181</td>
 
   <td align="center">-0.86842</td>
<font color="orange">where <math>~C_B</math> is a constant.</font> It is customary to define an effective potential which is the sum of the gravitational potential and the system's centrifugal potential (as viewed from the rotating frame), namely,
   <td align="center">-0.75709</td>
<div align="center">
   <td align="center">-0.43181</td>
<table border="0" cellpadding="5" align="center">
   <td align="center">-1.14704</td>
 
   <td align="center">+2.30682</td>
<tr>
   <td align="center">-5.3422</td>
   <td align="right">
<math>~\Phi_\mathrm{eff} \equiv \Phi_\mathrm{grav} + \Psi</math>
   </td>
   <td align="center">
<math>~=</math>
   </td>
   <td align="left">
<math>~
\Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)
- \frac{1}{2} \lambda^2(x^2 + y^2
+ \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) \, ,
</math>
   </td>
</tr>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (7)
</div>
in which case the statement of detailed force balance in Riemann S-type ellipsoids can be rewritten in the following deceptively simpler form:
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.641</td>
   <td align="right">
  <td align="center" bgcolor="pink">1.13137</td>
<math>~H + \Phi_\mathrm{eff}</math>
   <td align="center" bgcolor="pink">0.15077</td>
   </td>
   <td align="center"> - 0.30322</td>
   <td align="center">
  <td align="center">- 0.26801</td>
<math>~=</math>
   <td align="center">- 0.15077</td>
   </td>
   <td align="center">-1.13137</td>
   <td align="left">
  <td align="center">2.27531</td>
<math>~C_B \, .</math>
   <td align="center">- 15.0913</td>
   </td>
</tr>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eq. (8)
</div>
====Evaluation of the Gravitational Potential====
Drawing from a separate discussion of the [[User:Tohline/ThreeDimensionalConfigurations/HomogeneousEllipsoids#Gravitational_Potential|gravitational potential of homogeneous ellipsoids]], we see that for Riemann S-type ellipsoids,
<div align="center">
<math>
~\Phi_\mathrm{grav}(\vec{x}) = -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr],
</math><br />
[ [[User:Tohline/Appendix/References#EFE|EFE]], <font color="#00CC00">Chapter 3, Eq. (40)</font><sup>1,2</sup> ]<br />
[ [[User:Tohline/Appendix/References#BT87|BT87]], <font color="#00CC00">Chapter 2, Table 2-2</font> ]
</div>
where, the normalization constant,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.590</td>
   <td align="right">
  <td align="center" bgcolor="pink">1.10661</td>
<math>
  <td align="center" bgcolor="pink">0.06406</td>
~I_\mathrm{BT}
  <td align="center">-0.12883</td>
</math>
   <td align="center">-0.11642</td>
   </td>
   <td align="center">-0.06406</td>
   <td align="left">
  <td align="center">-1.10661</td>
<math>
  <td align="center">+2.22552</td>
~= A_1 + A_2\biggl(\frac{b}{a}\biggr)^2+ A_3\biggl(\frac{c}{a}\biggr)^2 .
   <td align="center">-34.7411</td>
</math>
   </td>
</tr>
</tr>
</table>
<div align="center">
[ [[User:Tohline/Appendix/References#EFE|EFE]], <font color="#00CC00">Chapter 3, Eq. (22)</font><sup>1</sup>]<br />
[ [[User:Tohline/Appendix/References#BT87|BT87]], <font color="#00CC00">Chapter 2, Table 2-2</font> ]
</div>
====Implied Parameter Values====
So, at the surface of the ellipsoid (where the enthalpy ''H = 0'') on each of its three principal axes, the equilibrium conditions demanded by the expression for detailed force balance become, respectively:
<ol type="I">
<li>On the x-axis, where (x, y, z) = (a, 0, 0):
<br />
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.564</td>
   <td align="right">
   <td align="center" bgcolor="pink">1.09034</td>
<math>~C_B</math>
   <td align="center" bgcolor="pink">0.02033</td>
   </td>
  <td align="center">-0.04089</td>
   <td align="center">
   <td align="center">-0.03750</td>
<math>~=</math>
   <td align="center">-0.02033</td>
   </td>
   <td align="center">-1.09034</td>
   <td align="left">
  <td align="center">+2.19279</td>
<math>~
   <td align="center">-107.86</td>
-\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_1 a^2   \biggr]
- \frac{1}{2} \Omega_f^2(a^2 )
- \frac{1}{2} \lambda^2(a^2) 
+ \Omega_f \lambda \biggl(\frac{b}{a}\cdot a^2 \biggr) 
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.538</td>
   <td align="right">
  <td align="center" bgcolor="pink">1.07148</td>
<math>~\Rightarrow ~~~2\biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT} \biggr]</math>
   <td align="center" bgcolor="pink">- 0.02324</td>
   </td>
   <td align="center">+0.04674</td>
   <td align="center">
  <td align="center">+0.04362</td>
<math>~=</math>
   <td align="center">+0.02324</td>
   </td>
   <td align="center">- 1.07148</td>
   <td align="left">
  <td align="center">+2.15487</td>
<math>~
   <td align="center">+92.722</td>
(2\pi G \rho) A_1  - \Omega_f^2 - \lambda^2  + 2\Omega_f \lambda \biggl(\frac{b}{a}  \biggr) 
</math>
   </td>
</tr>
</tr>
</table>
</li>
<li>On the y-axis, where (x, y, z) = (0, b, 0):
<br />
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.487</td>
   <td align="right">
   <td align="center" bgcolor="pink">1.02639</td>
<math>~C_B</math>
   <td align="center" bgcolor="pink">- 0.10880</td>
   </td>
  <td align="center">+0.21881</td>
   <td align="center">
   <td align="center">+0.21318</td>
<math>~=</math>
   <td align="center">+0.10880</td>
   </td>
  <td align="center">-1.02639</td>
   <td align="left">
  <td align="center">+2.06418</td>
<math>~
   <td align="center">+18.972</td>
-\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_2 b^2 \biggr]
- \frac{1}{2} \Omega_f^2(b^2)
- \frac{1}{2} \lambda^2(b^2) 
+ \Omega_f \lambda \biggl(\frac{a}{b}\cdot b^2 \biggr) 
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.333</td>
   <td align="right">
  <td align="center" bgcolor="pink">0.79257</td>
<math>~\Rightarrow ~~~ 2\biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT} \biggr]</math>
   <td align="center" bgcolor="pink">- 0.39224</td>
   </td>
   <td align="center">+0.78884</td>
   <td align="center">
  <td align="center">+0.99529</td>
<math>~=</math>
   <td align="center">+0.39224</td>
   </td>
   <td align="center">-0.79257</td>
   <td align="left">
  <td align="center">+1.59395</td>
<math>~
   <td align="center">+4.06370</td>
(2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr)
- \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr)
- \lambda^2\biggl( \frac{b^2}{a^2} \biggr)
+ 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr) 
</math>
   </td>
</tr>
</tr>
<tr>
</table>
  <td align="center" rowspan="4" bgcolor="white">0.28</td>
</li>
  <td align="center" bgcolor="pink">0.256</td>
<li>On the z-axis, where (x, y, z) = (0, 0, c):
  <td align="center" bgcolor="pink">0.80944</td>
<br />
  <td align="center" bgcolor="pink">0.03668</td>
<table border="0" cellpadding="5" align="center">
   <td align="center">-0.14127</td>
 
   <td align="center">-0.17453</td>
<tr>
   <td align="center">-0.03668</td>
   <td align="right">
   <td align="center">-0.80944</td>
<math>~C_B</math>
   <td align="center">+3.11750</td>
   </td>
   <td align="center">-84.992</td>
   <td align="center">
<math>~=</math>
   </td>
   <td align="left">
<math>~
-\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_3 c^2  \biggr]
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="yellow">0.245083</td>
   <td align="right">
  <td align="center" bgcolor="yellow">0.796512<sup>a</sup></td>
<math>~\Rightarrow ~~~ 2 \biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT}\biggr]</math>
   <td align="center" bgcolor="yellow">0.0</td>
   </td>
   <td align="center">0.0</td>
   <td align="center">
  <td align="center">0.0</td>
<math>~=</math>
  <td align="center">0.0</td>
   </td>
   <td align="center">&hellip;</td>
   <td align="left">
   <td align="center">&hellip;</td>
<math>~
  <td align="center"><math>~\infty</math></td>
(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)
</math>
  </td>
</tr>
</tr>
</table>
</li>
</ol>
Using the result from "III" to replace the left-hand side of both relation "I" and relation "II", we find that,
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.231</td>
   <td align="right">
  <td align="center" bgcolor="pink">0.77651</td>
<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>
  <td align="center" bgcolor="pink">- 0.04714</td>
   </td>
  <td align="center">+0.18156</td>
   <td align="center">
  <td align="center">+0.23381</td>
<math>~=</math>
  <td align="center">+0.04714</td>
   </td>
  <td align="center">-0.77651</td>
   <td align="left">
  <td align="center">+2.99067</td>
<math>~
   <td align="center">+63.442</td>
(2\pi G \rho) A_1  - \Omega_f^2 - \lambda^2  + 2\Omega_f \lambda \biggl(\frac{b}{a}  \biggr)  \, ,
</tr>
</math>
<tr>
   <td align="center" bgcolor="pink">0.205</td>
  <td align="center" bgcolor="pink">0.72853</td>
  <td align="center" bgcolor="pink">- 0.13511</td>
  <td align="center">+0.52037</td>
  <td align="center">+0.71427</td>
  <td align="center">+0.13511</td>
  <td align="center">-0.72853</td>
  <td align="center">+2.80588</td>
   <td align="center">+20.7674</td>
</tr>
<tr>
   <td align="left" colspan="10">
<sup>a</sup>According to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.
   </td>
   </td>
</tr>
</tr>
</table>
</table>


and,


===Our Parameter Determinations===
<table border="0" cellpadding="5" align="center">
The parameter values that have been posted above in our Table 1 are typically given with five digits of precision.  This is because, as explained, the values were determined from the ''analytically determined'' values, <math>~\omega_\mathrm{analytic}</math> and <math>~\lambda_\mathrm{analytic}</math>, that were provided by Ou (2006) with only five digit accuracy.  Our Table 2 (shown immediately below) provides values of this same set of model parameters to better than eleven digits accuracy.  We calculated these parameter values by following the steps detailed in earlier subsections of this chapter and, as a foundation, using double-precision versions of ''Numerical Recipes'' algorithms to evaluate the special functions, <math>~F(\phi,k)</math> and <math>~E(\phi,k)</math>.  As an example, the above pair of brief tables titled, ''TEST (part 1)'' and ''TEST (part 2)'' detail all of the intermediate steps that were used in order to determine the high-precision parameter values specifically for the model having the axis-ratio pair <math>~(0.9,0.641)</math>.  This table of higher precision parameter values was primarily generated in order to convince ourselves that we understood from first principles how to accurately determine the properties of Riemann S-type ellipsoids; the lower-precision parameter values that we derived from Ou's work provided a handy means of cross-checking these "first principles" determinations.
 
<span id="Table2">In generating our Table 2, we wondered what the approriate ''signs'' were of the various model parameters &#8212; especially when part of our objective is to distinguish between ''direct'' and ''adjunct'' configurations.  We took the following approach:  First we decided that the spin frequency of every ''direct'' configuration should be positive.  (Evidently, Ou made this same choice.)</span> 


<table border="1" align="center" cellpadding="8" width="90%">
<tr>
<tr>
   <td align="center" colspan="10">
  <td align="right">
<b>Table 2: &nbsp; Example Riemann S-type Ellipsoids</b> (double-precision evaluation)
<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>
  </td>
   <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
(2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr)
- \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr)
- \lambda^2\biggl( \frac{b^2}{a^2} \biggr)
+ 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr)  \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</div>
Multiplying the first of these two expressions by <math>~(b/a)^2</math> then subtracting it from the second gives,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
   <td align="right">
  <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr) - \biggl(\frac{b}{a}\biggr)^2 (2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>
   <td align="center" rowspan="1" colspan="4">
  </td>
Properties of<br /><b>''Direct'' Configurations</b>
   <td align="center">
<math>~=</math>
   </td>
   </td>
   <td align="center" rowspan="1" colspan="4">
   <td align="left">
Properties of<br /><b>''Adjoint'' Configurations</b>
<math>~
(2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr)
+ 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr)
- \biggl(\frac{b}{a}\biggr)^2 \biggl[ (2\pi G \rho) A_1    + 2\Omega_f \lambda \biggl(\frac{b}{a}  \biggr)  \biggr]
</math>
   </td>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" rowspan="1"><math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math></td>
   <td align="right">
   <td align="center" rowspan="1"><math>~\lambda</math></td>
<math>~\Rightarrow ~~~ \frac{(\pi G \rho)c^2}{ab} \biggl[  A_3 a^2  -  A_3 b^2  \biggr]</math>
   <td align="center" rowspan="1"><math>~\zeta </math></td>
   </td>
   <td align="center" rowspan="1"><math>~f \equiv \frac{\zeta}{\Omega}</math></td>
   <td align="center">
   <td align="center" rowspan="1"><math>~\omega^\dagger </math></td>
<math>~=</math>
  <td align="center" rowspan="1"><math>~\lambda^\dagger </math></td>
   </td>
  <td align="center" rowspan="1"><math>~\zeta^\dagger = \omega^\dagger f^\dagger</math></td>
   <td align="left">
   <td align="center" rowspan="1"><math>~f^\dagger </math></td>
<math>~
(\pi G \rho) (A_2 - A_1) a b
+ \Omega_f \lambda a^
- ab \biggl[ \Omega_f \lambda \biggl(\frac{b}{a}  \biggr)  \biggr]
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">(1)</td>
   <td align="right">
   <td align="center">(2)</td>
&nbsp;
   <td align="center">(3)</td>
   </td>
  <td align="center">(4)</td>
   <td align="center">
   <td align="center">(5)</td>
<math>~=</math>
   <td align="center">(6)</td>
   </td>
  <td align="center">(7)</td>
   <td align="left">
  <td align="center">(8)</td>
<math>~
  <td align="center">(9)</td>
(\pi G \rho) (A_2 - A_1) a b
   <td align="center">(10)</td>
+ \Omega_f \lambda ( a^2 -  b^2 )
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" rowspan="7" bgcolor="white">0.90</td>
   <td align="right">
  <td align="center" bgcolor="pink">0.795</td>
<math>~\Rightarrow ~~~
   <td align="center" bgcolor="white">+1.147036091720</td>
\frac{\Omega_f \lambda}{\pi G \rho}
   <td align="center" bgcolor="white">+0.431809451699</td>
</math>
  <td align="center">-0.868416786194</td>
   </td>
   <td align="center">-0.757096320116</td>
   <td align="center">
   <td align="center">-0.431809460593</td>
<math>~=</math>
  <td align="center">-1.147036104571</td>
   </td>
  <td align="center">+2.306817054749</td>
   <td align="left">
   <td align="center">-5.342210487323</td>
<math>~
\frac{1}{a b ( a^2 -  b^2 )}\biggl[ A_3 ( a^2  -  b^2 )c^2  -  (A_2 - A_1) a^2 b^2 \biggr] \, .
</math>
   </td>
</tr>
</tr>
</table>
Alternatively, just subtracting the first expression from the second gives,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.641</td>
   <td align="right">
   <td align="center" bgcolor="white">+1.131374738327</td>
<math>~0</math>
   <td align="center" bgcolor="white">+0.150771621841</td>
   </td>
  <td align="center"> -0.303218483925</td>
   <td align="center">
   <td align="center">-0.268008886644</td>
<math>~=</math>
   <td align="center">-0.150771621877</td>
   </td>
  <td align="center">-1.131374730590</td>
   <td align="left">
   <td align="center">+2.275320291519</td>
<math>~
   <td align="center">-15.091170863305</td>
(2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr)
- \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr)
- \lambda^2\biggl( \frac{b^2}{a^2} \biggr)
-
\biggl[ (2\pi G \rho) A_1  - \Omega_f^2 - \lambda^2   \biggr]</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.590</td>
   <td align="right">
   <td align="center" bgcolor="white">+1.106612583610</td>
&nbsp;
   <td align="center" bgcolor="white">+0.064060198174</td>
   </td>
  <td align="center">-0.128832176328</td>
   <td align="center">
   <td align="center">-0.116420305902</td>
<math>~=</math>
   <td align="center">-0.064060197762</td>
   </td>
  <td align="center">-1.106612576964</td>
   <td align="left">
  <td align="center">+2.225520849228</td>
<math>~
   <td align="center">-34.741086358509</td>
(2\pi G \rho) \biggl[ A_2 \biggl( \frac{b^2}{a^2}\biggr) - A_1  \biggr]
+ \Omega_f^2 \biggl[1 - \frac{b^2}{a^2}  \biggr] + \lambda^2 \biggl[1 - \frac{b^2}{a^2}  \biggr]</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.564</td>
   <td align="right">
  <td align="center" bgcolor="white">+1.090339840378</td>
<math>~\Rightarrow ~~~ \frac{\Omega_f^2 + \lambda^2}{\pi G \rho}  </math>
   <td align="center" bgcolor="white">+0.020334563779</td>
   </td>
   <td align="center">-0.040895067155</td>
   <td align="center">
  <td align="center">-0.037506716440</td>
<math>~=</math>
   <td align="center">-0.020334563809</td>
   </td>
   <td align="center">-1.090339837153</td>
   <td align="left">
  <td align="center">+2.192794561386</td>
<math>~
   <td align="center">-107.8358300897</td>
2 \biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] \, .
</math>
   </td>
</tr>
</tr>
</table>
We can eliminate <math>~\lambda</math> between these last two expressions as follows:  From the first of the two, we have
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.538</td>
   <td align="right">
  <td align="center" bgcolor="white">+1.071485625744</td>
<math>~
   <td align="center" bgcolor="white">-0.023236834336</td>
\lambda
   <td align="center">+0.046731855720</td>
</math>
  <td align="center">+0.043614077664</td>
   </td>
   <td align="center">+0.023236835120</td>
   <td align="center">
   <td align="center">-1.071485656401</td>
<math>~=</math>
  <td align="center">+2.154876708984</td>
   </td>
   <td align="center">+92.735376233270</td>
   <td align="left">
<math>~
\frac{1}{\Omega_f} \biggl\{ \frac{\pi G \rho}{a b ( a^2 -  b^2 )}\biggl[ A_3 ( a^2  -  b^2 )c^2  -  (A_2 - A_1) a^2 b^2 \biggr] \biggr\} \, .
</math>
   </td>
</tr>
</tr>
</table>
Hence, the second gives,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.487</td>
   <td align="right">
  <td align="center" bgcolor="white">+1.026387311947</td>
<math>~\Omega_f^2 </math>
   <td align="center" bgcolor="white">-0.108799837242</td>
   </td>
   <td align="center">+0.218808561563</td>
   <td align="center">
  <td align="center">+0.213183225210</td>
<math>~=</math>
   <td align="center">+0.108799835209</td>
   </td>
   <td align="center">-1.026387320039</td>
   <td align="left">
  <td align="center">+2.064178943634</td>
<math>~
   <td align="center">+18.972261524065</td>
2 (\pi G \rho)\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] - \lambda^2 
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.333</td>
   <td align="right">
   <td align="center" bgcolor="lightgreen">+0.792566980901</td>
&nbsp;
   <td align="center" bgcolor="lightgreen">-0.392440787995</td>
   </td>
  <td align="center">+0.789242029190</td>
   <td align="center">
   <td align="center">+0.995804846843</td>
<math>~=</math>
   <td align="center">+0.392440793882</td>
   </td>
   <td align="center">-0.792566979129</td>
   <td align="left">
  <td align="center">+1.593940258026</td>
<math>~
   <td align="center">+4.061606964516</td>
2 (\pi G \rho)\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] -    
\frac{1}{\Omega_f^2} \biggl\{ \frac{\pi G \rho}{a b ( a^2 -  b^2 )}\biggl[ A_3 ( a^2  -  b^2 )c^2  -  (A_2 - A_1) a^2 b^2 \biggr] \biggr\}^2
</math>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" rowspan="1" bgcolor="white">0.74</td>
   <td align="right">
  <td align="center" bgcolor="pink">0.692</td>
<math>~\Rightarrow ~~~ 0</math>
   <td align="center" bgcolor="lightgreen">+1.132149</td>
   </td>
   <td align="center" bgcolor="lightgreen">+0.385992</td>
   <td align="center">
  <td align="center">&nbsp;</td>
<math>~=</math>
   <td align="center">&nbsp;</td>
   </td>
   <td align="center">-0.385992</td>
   <td align="left">
   <td align="center">-1.132149</td>
<math>~ \frac{\Omega_f^4}{(\pi G \rho)^2}
  <td align="center">&nbsp;</td>
- \frac{2\Omega_f^2}{(\pi G \rho)} \biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] +    
   <td align="center">&nbsp;</td>
\biggl\{ \frac{1}{a b ( a^2 -  b^2 )}\biggl[ A_3 ( a^2  -  b^2 )c^2  -  (A_2 - A_1) a^2 b^2 \biggr] \biggr\}^2 \, .
</math>
   </td>
</tr>
</tr>
</table>
This is a quadratic equation whose solution gives <math>~\Omega_f^2/(\pi G \rho)</math> and, in turn,  <math>~\lambda^2/(\pi G \rho)</math>.  Specifically for ''Direct'' configurations, we find that,
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" rowspan="2" bgcolor="white">0.41</td>
   <td align="right">
   <td align="center" bgcolor="pink">0.385</td>
<math>~\frac{\Omega_f^2}{(\pi G \rho)}</math>
   <td align="center" bgcolor="lightgreen">+0.971082</td>
   </td>
  <td align="center" bgcolor="lightgreen">+0.141594</td>
   <td align="center">
   <td align="center">&nbsp;</td>
<math>~=</math>
   <td align="center">&nbsp;</td>
   </td>
  <td align="center">-0.141594</td>
   <td align="left">
   <td align="center">-0.971082</td>
<math>~\frac{1}{2} \biggl[M + \sqrt{ M^2 - 4N^2} \biggr] \, ,</math>
  <td align="center">&nbsp;</td>
   </td>
  <td align="center">&nbsp;</td>
<td align="center">&nbsp; &nbsp; &nbsp; and &nbsp; &nbsp; &nbsp;</td>
</tr>
   <td align="right">
<tr>
<math>~\frac{\lambda^2}{(\pi G \rho)}</math>
   <td align="center" bgcolor="pink">0.333</td>
   </td>
  <td align="center" bgcolor="white">+0.929630138695</td>
   <td align="center">
   <td align="center" bgcolor="white">+0.003311666790</td>
<math>~=</math>
   <td align="center">-0.009435019456</td>
   </td>
  <td align="center">-0.010149218281</td>
   <td align="left">
   <td align="center">-0.003311666699</td>
<math>~\frac{1}{2} \biggl[M - \sqrt{ M^2 - 4N^2} \biggr] \, ,</math>
   <td align="center">-0.929630099681</td>
   </td>
  <td align="center">+2.648538827896</td>
   <td align="center">-799.7601146950</td>
</tr>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 551, &sect;2, Eqs. (15) &amp; (16)
</div>
where,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center" rowspan="4" bgcolor="white">0.28</td>
   <td align="right">
  <td align="center" bgcolor="pink">0.256</td>
<math>~M</math>
   <td align="center" bgcolor="lightgreen">+0.809436834686</td>
   </td>
   <td align="center" bgcolor="lightgreen">+0.036676037913</td>
   <td align="center">
  <td align="center">-0.141255140305</td>
<math>~\equiv</math>
   <td align="center">-0.174510396110</td>
   </td>
   <td align="center">-0.036676038521</td>
   <td align="left">
  <td align="center">-0.809436833116</td>
<math>~
  <td align="center">+3.117488145828</td>
2\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] \, ,</math> &nbsp; &nbsp; and,
   <td align="center">-85.000678306244</td>
   </td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="yellow">0.245083</td>
   <td align="right">
  <td align="center" bgcolor="white">0.796512<sup>a</sup></td>
<math>~N</math>
   <td align="center" bgcolor="white">0.0</td>
   </td>
   <td align="center">0.0</td>
   <td align="center">
  <td align="center">0.0</td>
<math>~\equiv</math>
   <td align="center">0.0</td>
   </td>
  <td align="center">&hellip;</td>
   <td align="left">
   <td align="center">&hellip;</td>
<math>~
  <td align="center"><math>~\infty</math></td>
\frac{1}{a b ( a^2 -  b^2 )}\biggl[ A_3 ( a^2  -  b^2 )c^2  -  (A_2 - A_1) a^2 b^2 \biggr] \, .
</math>
  </td>
</tr>
</tr>
</table>
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <td align="center" bgcolor="pink">0.231</td>
   <td align="center" colspan="11"><b>TEST (part 3)</b></td>
  <td align="center" bgcolor="white">+0.776514825339</td>
  <td align="center" bgcolor="white">-0.047142035397</td>
  <td align="center">+0.181564182043</td>
  <td align="center">+0.233819345828</td>
  <td align="center">+0.047142037070</td>
  <td align="center">-0.776514835457</td>
  <td align="center">+2.990691423416</td>
  <td align="center">+63.440011724689</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center" bgcolor="pink">0.205</td>
   <td align="center" rowspan="1"><math>~\frac{b}{a}</math></td>
   <td align="center" bgcolor="white">+0.728526018042</td>
  <td align="center" rowspan="1"><math>~\frac{c}{a}</math></td>
   <td align="center" bgcolor="white">-0.135108121071</td>
   <td align="center" rowspan="1"><math>~A_1</math></td>
   <td align="center">+0.520359277725</td>
   <td align="center" rowspan="1"><math>~A_2</math></td>
   <td align="center">+0.714263156392</td>
   <td align="center" rowspan="1"><math>~A_3</math></td>
   <td align="center">+0.135108125079</td>
   <td align="center" rowspan="1"><math>~M</math></td>
   <td align="center">-0.728526039364</td>
   <td align="center" rowspan="1"><math>~N</math></td>
   <td align="center">+2.805866003036</td>
   <td align="center" rowspan="1"><math>~\frac{\Omega_f^2}{\pi G \rho}</math></td>
   <td align="center">+20.767558718483</td>
   <td align="center" rowspan="1"><math>~\frac{\lambda^2}{\pi G \rho}</math></td>
  <td align="center" rowspan="1"><math>~\frac{\Omega_f}{\sqrt{G \rho}}</math></td>
   <td align="center" rowspan="1"><math>~\frac{\lambda}{\sqrt{G \rho}}</math></td>
</tr>
</tr>
<tr>
<tr>
   <td align="left" colspan="10">
   <td align="center">0.9</td>
<sup>a</sup>According to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.
  <td align="center">0.641</td>
   </td>
  <td align="center">0.521450273</td>
  <td align="center">0.595131012</td>
  <td align="center">0.883418715</td>
  <td align="center">0.414682903</td>
  <td align="center">0.054301271</td>
  <td align="center">0.407446048</td>
  <td align="center">0.007236855</td>
  <td align="center">1.131383892</td>
   <td align="center">0.150782130</td>
</tr>
</tr>
</table>
</table>


=Feeding a 3D Animation=


==Initial Thoughts==
The numerical values listed in the last two columns of this "part 3" test match the values listed [[#TestPart2|above in "part 2" of our test]] for, respectively, <math>~\omega</math> and <math>~\omega^\dagger</math>.
 
===Relate EFE to Ou(2006)===


Let's examine the elliptical trajectory of a Lagrangian particle that is moving in the equatorial plane of a Riemann S-Type ellipsoid. As viewed in a frame that is spinning about the Z-axis at angular frequency, <math>~\Omega</math>, the trajectory is defined by,
As we have already acknowledged, according to [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)], at any coordinate position inside or on the surface of the ellipsoid, <math>~(x, y)</math>, the three components of the velocity as viewed from a frame of rotation that is spinning at the equilibrium configuration's frequency, <math>~\Omega_f</math>, are,
<table border="0" cellpadding="5" align="center">


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~{\vec{v}}_\mathrm{rot}</math>
r^2
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>
<math>~=</math>
~=
</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~\lambda \biggl( \frac{ay}{b} , - \frac{bx}{a} , 0 \biggr) \, ,</math>
\biggl(\frac{x}{a} \biggr)^2 + \biggl(\frac{y}{b}\biggr)^2 \, ,
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
where <math>~0 < r \le 1</math>.  (The surface of the relevant ellipsoid is associated with the value, <math>~r=1</math>.)


Let's choose a pair of axis ratios &#8212; for example, <math>~b/a = 0.28</math> and <math>~c/a = 0.231</math> &#8212; then, from Table 1 of our [[#Models_Examined_by_Ou_.282006.29|above discussion]], draw the associated value of either <math>~\lambda</math> or <math>~\zeta</math> that corresponds to the Jacobi-like equilibrium configuration &#8212; in this example, <math>~\lambda = -0.04714</math> and <math>~\zeta = +0.18156</math>.  Then, for any point <math>~(x,y)</math> inside of the ellipsoid, the fluid's velocity components (as viewed from the rotating frame of reference) are,
where, <math>~\lambda</math> is an overall scale factor. But, according to &sect;48 of EFE, we see that,
<div align="center">
<table border="0" cellpadding="5" align="center">


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~\vec{u}</math>
v_x  = \frac{dx}{dt}  = \lambda \biggl( \frac{ay}{b} \biggr) = -0.16836 ~y
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~\biggl( Q_1 y , Q_2 x , 0 \biggr) \, ,</math>
v_y  = \frac{dy}{dt}  = - \lambda \biggl( \frac{bx}{a} \biggr) = + 0.01320~x \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>


Alternatively, we have,
[https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)], p. 892, &sect;II, Eq. (9)
</div>
where,
<div align="center">
<table border="0" cellpadding="5" align="center">


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~Q_1</math>
u_x = \frac{dx}{dt} = Q_1  y = - \biggl[ 1 + \frac{b^2}{a^2} \biggr]^{-1}\zeta ~y = -0.16836 ~y
  </td>
</math>
  <td align="center">
<math>~\equiv</math>
  </td>
  <td align="left">
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>
  </td>
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp; </td>
  <td align="right">
<math>~Q_2</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~\equiv</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta \, ,</math>
u_y  = \frac{dy}{dt}= Q_2 x  = + \biggl[ 1 + \frac{a^2}{b^2} \biggr]^{-1}\zeta ~x = + 0.01320~x \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>


Now, each Lagrangian fluid element's motion is oscillatory in both the <math>~x</math> and <math>~y</math> coordinate directionsSo let's see how this plays out.  Suppose,
[https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)], p. 892, &sect;II, Eq. (10)
</div>
and  <math>~\zeta</math> is the scalar magnitude of the vorticity vector, <math>~\vec\zeta</math>.  The transformation from EFE's notation to the one used by Ou is, then,
<table border="0" cellpadding="5" align="center">


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~\lambda \biggl( \frac{a}{b} \biggr) </math>
x = x_\mathrm{max} \cos(\varphi t)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>
y = y_\mathrm{max} \sin(\varphi t) \, .
</math>
   </td>
   </td>
</tr>
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp; </td>
</table>
 
Then,
 
<table align="center" border=0 cellpadding="3">
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~- \lambda \biggl( \frac{b}{a} \biggr) </math>
\frac{dx}{dt} = - x_\mathrm{max}\varphi \sin(\varphi t) = -  \biggl( \frac{x_\mathrm{max}}{y_\mathrm{max}}\biggr) \varphi y = - \varphi \biggl(\frac{ay}{b}\biggr)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta </math>
\frac{dy}{dt} = y_\mathrm{max} \varphi \cos(\varphi t) = + \biggl( \frac{y_\mathrm{max}}{x_\mathrm{max}}\biggr) \varphi x = + \varphi \biggl(\frac{bx}{a}\biggr) \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
<table border="0" cellpadding="5" align="center">


Hence our functional representation of the time-dependent behavior of both <math>~x</math> and <math>~y</math> works perfectly if, for each orbit inside of or on the surface of the configuration, we set <math>~\varphi = - \lambda</math> and if the ratio <math>~y_\mathrm{max}/x_\mathrm{max} = (b/a)</math>.  Hooray!
==Preferred Normalizations==
Let's do this again, assuming that <math>~x</math> and <math>~y</math> both have units of length and that <math>~t</math> has the unit of time.  Then, let's use <math>~a</math> to normalize lengths and use <math>~(\pi G \rho)^{-1 / 2}</math> to normalize time. We therefore have,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~\Rightarrow ~~~ \lambda </math>
\frac{x}{a} = \biggl(\frac{ x_\mathrm{max} }{a}\biggr) \cos\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}}  \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr]
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~- \biggl[ \frac{a b}{a^2 + b^2} \biggr]\zeta = - \biggl[ \frac{b}{a} + \frac{a}{b} \biggr]^{-1} \zeta\, ,</math>
\frac{y}{a} = \biggl(\frac{ y_\mathrm{max} }{a}\biggr) \sin\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}}  \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr] \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
 
which, gratifyingly agrees with Ou's equation (17).  It is worth noting as well that, when viewed from the inertial reference frame, the velocity field is,
 
<div align="center">
<table border="1" cellpadding="10" width="80%" align="center"><tr><td align="left">
<font color="red">'''NOTE:'''</font> &nbsp; When implementing in an xml-based COLLADA (3D animation) file, we associate <math>~\mathrm{TIME} = 4</math> with <math>~t \cdot (\pi G \rho)^{1 / 2} = 2\pi</math>Hence we can everywhere replace <math>~t \cdot (\pi G \rho)^{1 / 2}</math> with (in ''radians'') <math>~(\pi/2)\cdot \mathrm{TIME}</math> or (in ''degrees'') <math>~90 \cdot \mathrm{TIME}</math>.
 
<br />
This also means that, if <math>~\varphi/(\pi G \rho)^{1 / 2} = 1</math>,  each Lagrangian fluid element will move through one complete orbit (as viewed from a frame that is rotating with the ellipsoidal figure) in the time it takes the hand of the wall-mounted clock to complete one cycle.
</td></tr></table>
 
Next, let's normalize the velocities such that <math>~\rho</math> and the total mass, <math>~M</math>, are both assumed to be the same in every examined Riemann ellipsoid.  In particular, we will normalize to,
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~v_0</math>
<math>~\vec{v}</math>
  </td>
  <td align="center">
<math>~\equiv</math>
  </td>
  <td align="left">
<math>~(abc)^{1 / 3}(\pi G \rho)^{1 / 2}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 955: Line 1,210:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~a(\pi G \rho)^{1 / 2} \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{1 / 3} \, ,</math>
<math>~{\vec{v}}_\mathrm{rot} + \vec\Omega_f \times \vec{x} \, .</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
in which case we have,


<table align="center" border=0 cellpadding="3">
[https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)], p. 892, &sect;II, Eq. (13)
</div>
Broken down into its Cartesian components, this is
<div align="center">
<table border="0" cellpadding="5" align="center">
 
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
<math>~\vec{v}</math>
\frac{1}{v_0} \cdot \frac{dx}{dt} =  - \frac{\varphi}{(\pi G \rho)^{1 / 2} } \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~
\frac{1}{v_0} \cdot \frac{dy}{dt} =  + \frac{\varphi}{(\pi G \rho)^{1 / 2} }  \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3}  \cdot \biggl(\frac{x}{a}\biggr) \, .
\boldsymbol{\hat\imath} \biggl[\lambda \biggl( \frac{a}{b} \biggr) - \Omega_f  \biggr]y
+
\boldsymbol{\hat\jmath} \biggl[- \lambda \biggl( \frac{b}{a} \biggr) + \Omega_f  \biggr]x
</math>
</math>
   </td>
   </td>
</tr>
</tr>
</table>
Finally, setting, <math>~\varphi/(\pi G\rho)^{1 / 2} \rightarrow -\lambda_\mathrm{EFE}</math> means,


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>
&nbsp;
V_x \equiv \frac{1}{v_0} \cdot \frac{dx}{dt} \lambda_\mathrm{EFE} \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr)
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\boldsymbol{\hat\imath} \biggl[- \biggl( \frac{a b}{a^2 + b^2} \biggr)\zeta \biggl( \frac{a}{b} \biggr) - \Omega_f  \biggr]y
+
\boldsymbol{\hat\jmath} \biggl[\biggl( \frac{a b}{a^2 + b^2} \biggr)\zeta\biggl( \frac{b}{a} \biggr) + \Omega_f  \biggr]x
</math>
</math>
  </td>
</tr>
<tr>
  <td align="right">
&nbsp;
   </td>
   </td>
   <td align="center">
   <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
<math>~=</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~
V_y \equiv \frac{1}{v_0} \cdot \frac{dy}{dt} = - \lambda_\mathrm{EFE}  \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3}  \cdot \biggl(\frac{x}{a}\biggr) \, .
-\boldsymbol{\hat\imath} \biggl[ \biggl( \frac{a^2}{a^2 + b^2} \biggr) f  +  1 \biggr] \Omega_fy
+
\boldsymbol{\hat\jmath} \biggl[\biggl( \frac{b^2}{a^2 + b^2} \biggr) f  + 1  \biggr] \Omega_fx \, .
</math>
</math>
   </td>
   </td>
Line 998: Line 1,270:
</table>
</table>


==Example Mach Surface==
[https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract Chandrasekhar (1965)], p. 892, &sect;II, Eq. (14)
</div>
 
===Summary===
 
<span id="Fig1">It is often useful to discuss</span> the properties of Riemann S-type ellipsoids in the context of what we will refer to as the traditional "EFE Diagram" &#8212; a two-dimensional parameter space defined by the axis ratio ranges, 0 &le; b/a &le; 1 and 0 &le; c/a &le; 1.  It is useful to appreciate at the outset, for example, that Riemann S-type ellipsoids only populate a subset of the EFE Diagram's entire parameter space.  More specifically, they all lie between or on the two (self-adjoint) curves marked "X = -1" and "X = +1" in the EFE Diagram that is shown here, on the right.  Keeping this in mind, we summarize here a sequence of steps that should be taken in order to construct and thereby quantitatively detail all of the physical properties that are associated with any Riemann S-type ellipsoid that lies in this allowed region of the EFE Diagram.


Let's try to plot the "Mach surface" for the example model, b41c385, referenced below.  Its relevant parameter values are,
<table border="0" align="right" cellpadding="5">
<ul>
<tr><td align="center">'''Figure 1'''</td></tr>
  <li><math>~b/a = 0.41</math></li>
<tr><td align="center">
  <li><math>~c/a = 0.385</math></li>
[[File:EFEdiagram02.png|right|350px|EFE Diagram]]
  <li><math>~\lambda_\mathrm{EFE} = 0.079886</math></li>
</td></tr>
</ul>
<tr><td align="center">Caption:  See [[#Fig2|Figure 2, below]]</td></tr>
Hence, if we set a = 1 then we have,
</table>
<ol>
<li>Specify numerical values for any two of the three key parameters:  <math>~b/a, c/a, f \equiv \zeta/\Omega_f</math>.  The value of the third (unspecified) parameter can then be found by determining the root(s) of the [[#Based_on_Virial_Equilibrium|virial-equilibrium-based expression]],
<table border="0" cellpadding="5" align="center">


<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right"><math>~V_x</math></td>
   <td align="right">
   <td align="center"><math>=</math></td>
<math>~0</math>
   <td align="left"><math>~(0.079886) \biggl(\frac{1}{0.41}\biggr)\biggl( 1.85034 \biggr) \cdot y</math></td>
  </td>
  <td align="center">&nbsp; &nbsp; &nbsp;and&nbsp; &nbsp; &nbsp;</td>
   <td align="center">
  <td align="right"><math>~V_y</math></td>
<math>~=</math>
  <td align="center"><math>=</math></td>
  </td>
  <td align="left"><math>~- (0.079886)  \biggl(0.41\biggr) \biggl( 1.85034 \biggr)  \cdot x</math></td>
   <td align="left">
<math>~
\biggl[ \frac{a^2 b^2}{(a^2 + b^2)^2} \biggr] f^2
+ \biggl[ \frac{2a^2 b^2 B_{12}}{c^2 A_3 - a^2 b^2 A_{12}} \biggr]\frac{f}{a^2 + b^2} + 1 \, .
</math>
  </td>
</tr>
</tr>
<tr><td align="center" colspan="3">[ [[User:Tohline/Appendix/References#EFE|EFE]], <font color="#00CC00">&sect;48, Eq. (35)</font> ]</td></tr>
</table>
<ol type="A">
<li>If you specified the values of <math>~b/a</math> and <math>~c/a</math>, then values of the three parameters, <math>~A_1, A_2, A_3</math> &#8212; as well as the related parameters, <math>~A_{12}, B_{12}</math> &#8212; can be immediately determined from the [[#General_Coefficient_Expressions|above general coefficient expressions]] and [[#A12B12|related relations]] as long as you have an algorithm that can be used to evaluate incomplete elliptic integrals of the first and second kind. The governing virial-equilibrium-based expression then becomes a quadratic equation whose pair of roots give two physically viable values of the parameter, <math>~f</math>; we will refer to them as <math>~f_+</math> and <math>~f_-</math>
<br />NOTE:  If the chosen pair of axis ratios places your configuration ''above'' the Jacobi/Dedekind sequence in the familiar "EFE Diagram," then the parameter, <math>~f</math>, will invariably be negative; if it is ''below'' the Jacobi/Dedekind sequence, <math>~f</math> will invariably be positive. <br />NOTE as well:  This is the method that we have used, below, in order to replicate various equilibrium configurations that have been [[#Models_Examined_by_Ou_.282006.29|studied by Ou (2006)]].
</li>
<li>If, instead, you specified the value of <math>~f</math> and (only) one of the ellipsoid's axis ratios, then an iterative numerical scheme &#8212; such as a [https://brilliant.org/wiki/newton-raphson-method/ Newton Raphson method] &#8212; will need to be used in order to determine a physically viable (real) root of this nonlinear, virial-equilibrium-based expression.  This root will provide the value of the equilibrium ellipsoid's other axis ratio. 
<br />NOTE:  The [[User:Tohline/ThreeDimensionalConfigurations/JacobiEllipsoids#Jacobi_Ellipsoids|Jacobi/Dedelind sequence]] is determined in this manner by setting <math>~f = 0</math>, then determining what value of the c/a axis ratio is consistent with various selected values of 0 < b/a &le; 1.
</li>
<li>If, as in step 1.B, only one value of the parameter, <math>~f</math>, is known, the other relevant value may be obtained from the relation,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">&nbsp;</td>
   <td align="right">
  <td align="center"><math>=</math></td>
<math>~f_+ \cdot f_-</math>
   <td align="left"><math>~0.3605 y</math></td>
   </td>
   <td align="center">&nbsp; </td>
   <td align="center">
  <td align="right">&nbsp;</td>
<math>~=</math>
  <td align="center"><math>=</math></td>
  </td>
   <td align="left"><math>~- 0.0606 x</math></td>
   <td align="left">
<math>~
\biggl[ \frac{a^2 + b^2}{ab}\biggr]^2 \, .
</math>
  </td>
</tr>
</tr>
</table>
</table>
In either case, if <math>~|f_\pm | < 1</math> the model will be referred to as being a ''Jacobi-like'' &#8212; or, ''Direct'' &#8212; configuration because the magnitude of the configuration's spin frequency, <math>~|\Omega_f|</math>, is larger than the magnitude of the frequency, <math>~|\zeta|</math>, that characterizes internal motions (vorticity).  On the other hand, if <math>~|f_\pm | > 1</math> the model will be referred to as being a ''Dedekind-like'' &#8212; or, ''Adjoint'' &#8212; configuration because the internal motions dominate.
<br />NOTE:  A so-called ''self-adjoint'' model sequence will arise when <math>~f_+ = f_-</math> for all values of the axis ratio, 0 < b/a &le; 1.  There are two such sequences, namely, when <math>~f_+ = f_- = (a^2 + b^2)/(ab)</math> &#8212; this is the curve labeled, "X =+1" in the EFE Diagram shown here on the right &#8212; or when <math>~f_+ = f_- = -(a^2 + b^2)/(ab)</math> &#8212; this is the curve labeled, "X = - 1.  In the familiar EFE diagram, these curves intersect the Maclaurin sequence (where, b/a = 1) when, respectively, <math>~f_+ = +2</math> and <math>~f_+ = -2</math>. 
</li>
</ol>
</li>
<li>
Once a consistently specified set of parameters, <math>~b/a, c/a</math> and <math>~f</math>, is known, the configuration's spin frequency may be straightforwardly obtained from another [[#Based_on_Virial_Equilibrium|virial-equilibrium-based expression]], namely,
<table border="0" cellpadding="5" align="center">


Borrowing from an [[User:Tohline/Appendix/Ramblings/RiemannB74C692#location_X|accompanying discussion]], we have the following example data set.
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <th align="center" colspan="11">''Direct''</th>
   <td align="right">
</tr>
<math>~\frac{\Omega_f^2}{\pi G \rho}</math>
<tr>
  </td>
   <td align="center" rowspan="2">n</td>
   <td align="center">
   <td align="center" colspan="2">Axisymmetric</td>
<math>~=</math>
   <td align="center" colspan="1">b41c385</td>
   </td>
  <td align="center" colspan="3" bgcolor="lightblue">Surface</td>
   <td align="left">
   <td align="center" colspan="3">|V| = 0.1</td>
<math>~2B_{12} \biggl[ 1 + \frac{a^2 b^2 \cdot f^2}{(a^2 + b^2)^2}  \biggr]^{-1} \, .</math>
   </td>
</tr>
</tr>
<tr><td align="center" colspan="3">[ [[User:Tohline/Appendix/References#EFE|EFE]], <font color="#00CC00">&sect;48, Eq. (33)</font> ]</td></tr>
</table>
</li>
<li>
Once a consistently specified pair of parameters, <math>~\Omega_f</math> and <math>~f</math>, is known, the configuration's vorticity can immediately be determined via the expression,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center">x<sub>0</sub></td>
   <td align="right">
   <td align="center">y<sub>0</sub></td>
<math>~\vec\zeta = \boldsymbol{\hat{k}} \zeta </math>
   <td align="center">y = 0.41 &times; y<sub>0</sub></td>
   </td>
   <td align="center">V<sub>x</sub></td>
   <td align="center">
   <td align="center">V<sub>y</sub></td>
&nbsp; &nbsp; where, &nbsp; &nbsp;
  <td align="center">|V|</td>
   </td>
  <td align="center">''factor''</td>
   <td align="left">
  <td align="center">x</td>
<math>~\zeta = (f \Omega_f) \, .</math> </td>
  <td align="center">y</td>
</tr>
</tr>
</table>
</li>
<li>
At every location inside a Riemann S-type ellipsoid, the fluid vorticity must be related to the underlying velocity field via the expression, <math>~\vec\zeta = \nabla \times {\vec{v}}_\mathrm{rot}</math>.  In order for the vorticity to be uniform throughout the configuration &#8212; everywhere being represented by the vector, <math>~\vec\zeta = \boldsymbol{\hat{k}} \zeta</math> &#8212; we realize that the velocity field is properly described by the expression,
<div align="center">
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="center">1</td>
   <td align="right">
  <td align="right">1.0000</td>
<math>~{\vec{v}}_\mathrm{rot}</math>
   <td align="right">0.0000</td>
   </td>
   <td align="right">0.0000</td>
   <td align="center">
  <td align="right" bgcolor="lightblue">0.0000</td>
<math>~=</math>
  <td align="right">-0.0606</td>
   </td>
   <td align="right">0.0606</td>
   <td align="left">
   <td align="center">---</td>
<math>~\lambda \biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \biggl(\frac{b}{a}\biggr)x \biggr]  \, ,</math>
  <td align="center">---</td>
   </td>
   <td align="center">---</td>
<td align="center">&nbsp; &nbsp; &nbsp; where, &nbsp; &nbsp; &nbsp;</td>
</tr>
   <td align="right">
<tr>
<math>~\lambda</math>
  <td align="center">2</td>
   </td>
   <td align="right">0.9921</td>
   <td align="center">
  <td align="right">-0.1253</td>
<math>~\equiv</math>
   <td align="right">-0.0514</td>
   </td>
   <td align="right" bgcolor="lightblue">-0.0185</td>
   <td align="left">
  <td align="right">-0.0601</td>
<math>~- \biggl[ \frac{ab}{a^2 + b^2} \biggr] \zeta \, .</math>
   <td align="right">0.0629</td>
   </td>
   <td align="center">---</td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
</table>
[https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou(2006)], p. 550, &sect;2, Eqs. (3) &amp; (17)
</div>
</li>
</ol>
==Models Examined by Ou (2006)==
In &sect;2 of [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)], immediately after equation (6), we find the following declaration: &nbsp; In ''direct'' configurations, &omega; > &lambda; so the fluid motion is dominated by figure rotation; conversely, in an ''adjoint'' configuration, &omega; < &lambda; so the fluid motion is dominated by internal motions.
===His Tabulated Model Parameters===
Table 1 (see below) lists a subset of the Riemann S-type ellipsoids that were studied by [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)]; properties of various so-called ''Direct'' configurations can be found in Ou's Table 1, while properties of various ''Adjoint'' configurations can be found in his Table 5.  Each row of ''our'' Table 1 was constructed as follows:
<ul>
  <li>The pair of axis ratios <math>~(\tfrac{b}{a}, \tfrac{c}{a} )</math> associated with one of Ou's (2006) uniform-density, incompressible <math>~(n=0)</math> ellipsoid models (columns 1 and 2 from Ou's Table 1) has been copied into columns 1 and 2 of ''our'' table.</li>
  <li>Properties of ''Direct Configurations'' &hellip;</li>
  <ul>
    <li>The pair of parameter values <math>~(\omega_\mathrm{analytic}, \lambda_\mathrm{analytic})</math> that is required in order for this to be an <b>equilibrium</b> configuration &#8212; as specified by the above set of analytical expressions from EFE &#8212; is copied from, respectively, columns 11 and 13 of Ou's Table 1 into columns 3 and 4 of ''our'' table; in our table, the "analytic" subscript has been dropped from the column headings.</li>
    <li>The value of the equilibrium configuration's vorticity, <math>~\zeta</math> &#8212; see column 5 of our table &#8212; has been determined from the expression,<br /><table border="0" align="center"><tr><td align="center"><math>~\zeta = - \biggl[ \frac{1 + (b/a)^2}{b/a} \biggr] \lambda \, .</math></td></tr></table></li>
    <li>Column 6 of our table lists the value of the frequency ratio, <math>~f \equiv \zeta/\omega</math>.
  </ul>
  <li>Properties of ''Adjoint Configurations'' [in order to distinguish from ''Direct'' configuration properties, a superscript &dagger; has been attached to each parameter name] &hellip;</li>
  <ul>
    <li>As listed in column 7 of our Table, the "spin" angular velocity of the ''adjoint'' equilibrium configuration has been determined from the vorticity of the ''direct'' configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~\omega^\dagger = \zeta \biggl[\frac{b/a}{1 + (b/a)^2}\biggr] \, .</math></td></tr></table></li>
    <li>As listed in column 10 of our Table, the ratio <math>~(f^\dagger)</math> of the vorticity to the angular velocity in the ''adjoint'' equilibrium configuration has been determined from the same ratio <math>~(f)</math> in the ''direct'' configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~f^\dagger = \frac{1}{f} \biggl\{ \frac{[1 + (b/a)^2]^2}{(b/a)^2} \biggr\} \, .</math></td></tr></table></li>
  <li>As indicated, the value of the vorticity in the ''adjoint'' equilibrium configuration (column 9 of our table) has been determined from a product of <math>~\omega^\dagger</math> and <math>~f^\dagger</math>.</li>
    <li>As listed in column 8 of our table, the value of the parameter, <math>~\lambda^\dagger</math>, has been determined from the vorticity in the ''adjoint'' equilibrium configuration via the relation, <br /><table border="0" align="center"><tr><td align="center"><math>~\lambda^\dagger = -~ \zeta^\dagger \biggl[ \frac{b}{a} + \frac{a}{b}\biggr]^{-1} \, .</math></td></tr></table></li>
  </ul>
</ul>
<table border="1" align="center" cellpadding="8" width="90%">
<tr>
<tr>
   <td align="center">3</td>
   <td align="center" colspan="10">
  <td align="right">0.9686</td>
<b>Table 1: &nbsp; Example Riemann S-type Ellipsoids</b><br />
  <td align="right">-0.2487</td>
[Cells with a pink background contain numbers copied directly from Table 1 of [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)]]<br />
  <td align="right">-0.1020</td>
[Cells with a yellow background contain numbers drawn from Table IV (p. 103) of EFE]
  <td align="right" bgcolor="lightblue">-0.0368</td>
   </td>
  <td align="right">-0.0587</td>
  <td align="right">0.0693</td>
  <td align="center">---</td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">4</td>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
  <td align="right">0.9298</td>
   <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
   <td align="right">-0.3681</td>
   <td align="center" rowspan="1" colspan="4">
  <td align="right">-0.1509</td>
Properties of<br /><b>''Direct'' Configurations</b>
   <td align="right" bgcolor="lightblue">-0.0544</td>
   </td>
  <td align="right">-0.0563</td>
   <td align="center" rowspan="1" colspan="4">
   <td align="right">0.0783</td>
Properties of<br /><b>''Adjoint'' Configurations</b>
   <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">5</td>
   <td align="center" rowspan="1"><math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math></td>
   <td align="right">0.8763</td>
   <td align="center" rowspan="1"><math>~\lambda</math></td>
   <td align="right">-0.4818</td>
   <td align="center" rowspan="1"><math>~\zeta </math></td>
  <td align="right">-0.1975</td>
   <td align="center" rowspan="1"><math>~f \equiv \frac{\zeta}{\omega}</math></td>
   <td align="right" bgcolor="lightblue">-0.0712</td>
   <td align="center" rowspan="1"><math>~\omega^\dagger </math></td>
   <td align="right">-0.0531</td>
   <td align="center" rowspan="1"><math>~\lambda^\dagger </math></td>
  <td align="right">0.0888</td>
   <td align="center" rowspan="1"><math>~\zeta^\dagger = \omega^\dagger f^\dagger</math></td>
   <td align="center">---</td>
   <td align="center" rowspan="1"><math>~f^\dagger </math></td>
   <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">6</td>
   <td align="center">(1)</td>
   <td align="right">0.8090</td>
   <td align="center">(2)</td>
   <td align="right">-0.5878</td>
   <td align="center">(3)</td>
   <td align="right">-0.2410</td>
   <td align="center">(4)</td>
   <td align="right" bgcolor="lightblue">-0.0869</td>
   <td align="center">(5)</td>
   <td align="right">-0.0490</td>
   <td align="center">(6)</td>
   <td align="right">0.0998</td>
   <td align="center">(7)</td>
   <td align="center">---</td>
   <td align="center">(8)</td>
   <td align="center">---</td>
   <td align="center">(9)</td>
   <td align="center">---</td>
   <td align="center">(10)</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">7</td>
   <td align="center" rowspan="7" bgcolor="white">0.90</td>
   <td align="right">0.7290</td>
   <td align="center" bgcolor="pink">0.795</td>
   <td align="right">-0.6845</td>
   <td align="center" bgcolor="pink">1.14704</td>
   <td align="right">-0.2807</td>
   <td align="center" bgcolor="pink">0.43181</td>
   <td align="right" bgcolor="lightblue">-0.1012</td>
   <td align="center">-0.86842</td>
   <td align="right">-0.0442</td>
   <td align="center">-0.75709</td>
   <td align="right">0.1104</td>
   <td align="center">-0.43181</td>
   <td align="center">0.9058</td>
   <td align="center">-1.14704</td>
   <td align="center">0.6603</td>
   <td align="center">+2.30682</td>
   <td align="center">-0.2543</td>
   <td align="center">-5.3422</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">8</td>
   <td align="center" bgcolor="pink">0.641</td>
  <td align="right">0.6374</td>
   <td align="center" bgcolor="pink">1.13137</td>
   <td align="right">-0.7705</td>
   <td align="center" bgcolor="pink">0.15077</td>
   <td align="right">-0.3159</td>
   <td align="center"> - 0.30322</td>
   <td align="right" bgcolor="lightblue">-0.1139</td>
   <td align="center">- 0.26801</td>
   <td align="right">-0.0386</td>
   <td align="center">- 0.15077</td>
   <td align="right">0.1203</td>
   <td align="center">-1.13137</td>
   <td align="center">0.8313</td>
   <td align="center">2.27531</td>
   <td align="center">0.5298</td>
   <td align="center">- 15.0913</td>
   <td align="center">-0.2626</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">9</td>
   <td align="center" bgcolor="pink">0.590</td>
  <td align="right">0.5358</td>
   <td align="center" bgcolor="pink">1.10661</td>
   <td align="right">-0.8443</td>
   <td align="center" bgcolor="pink">0.06406</td>
   <td align="right">-0.3462</td>
   <td align="center">-0.12883</td>
   <td align="right" bgcolor="lightblue">-0.1248</td>
   <td align="center">-0.11642</td>
   <td align="right">-0.0325</td>
   <td align="center">-0.06406</td>
   <td align="right">0.1290</td>
   <td align="center">-1.10661</td>
   <td align="center">0.7752</td>
   <td align="center">+2.22552</td>
   <td align="center">0.4153</td>
   <td align="center">-34.7411</td>
   <td align="center">-0.2684</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">10</td>
   <td align="center" bgcolor="pink">0.564</td>
  <td align="right">0.4258</td>
   <td align="center" bgcolor="pink">1.09034</td>
   <td align="right">-0.9048</td>
   <td align="center" bgcolor="pink">0.02033</td>
   <td align="right">-0.3710</td>
   <td align="center">-0.04089</td>
   <td align="right" bgcolor="lightblue">-0.1337</td>
   <td align="center">-0.03750</td>
   <td align="right">-0.0258</td>
   <td align="center">-0.02033</td>
   <td align="right">0.1362</td>
   <td align="center">-1.09034</td>
   <td align="center">0.7342</td>
   <td align="center">+2.19279</td>
   <td align="center">0.3126</td>
   <td align="center">-107.86</td>
   <td align="center">-0.2724</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">11</td>
   <td align="center" bgcolor="pink">0.538</td>
  <td align="right">0.3090</td>
   <td align="center" bgcolor="pink">1.07148</td>
   <td align="right">-0.9511</td>
   <td align="center" bgcolor="pink">- 0.02324</td>
   <td align="right">-0.3899</td>
   <td align="center">+0.04674</td>
   <td align="right" bgcolor="lightblue">-0.1406</td>
   <td align="center">+0.04362</td>
   <td align="right">-0.0187</td>
   <td align="center">+0.02324</td>
   <td align="right">0.1418</td>
   <td align="center">- 1.07148</td>
   <td align="center">0.7052</td>
   <td align="center">+2.15487</td>
   <td align="center">0.2179</td>
   <td align="center">+92.722</td>
   <td align="center">-0.2750</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">12</td>
   <td align="center" bgcolor="pink">0.487</td>
  <td align="right">0.1874</td>
   <td align="center" bgcolor="pink">1.02639</td>
   <td align="right">-0.9823</td>
   <td align="center" bgcolor="pink">- 0.10880</td>
   <td align="right">-0.4027</td>
   <td align="center">+0.21881</td>
   <td align="right" bgcolor="lightblue">-0.1452</td>
   <td align="center">+0.21318</td>
   <td align="right">-0.0114</td>
   <td align="center">+0.10880</td>
   <td align="right">0.1456</td>
   <td align="center">-1.02639</td>
   <td align="center">---</td>
   <td align="center">+2.06418</td>
   <td align="center">---</td>
   <td align="center">+18.972</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center">13</td>
   <td align="center" bgcolor="pink">0.333</td>
  <td align="right">0.0628</td>
   <td align="center" bgcolor="pink">0.79257</td>
   <td align="right">-0.9980</td>
   <td align="center" bgcolor="pink">- 0.39224</td>
   <td align="right">-0.4092</td>
   <td align="center">+0.78884</td>
   <td align="right" bgcolor="lightblue">-0.1475</td>
   <td align="center">+0.99529</td>
   <td align="right">-0.0038</td>
   <td align="center">+0.39224</td>
   <td align="right">0.1476</td>
   <td align="center">-0.79257</td>
   <td align="center">---</td>
   <td align="center">+1.59395</td>
   <td align="center">---</td>
   <td align="center">+4.06370</td>
   <td align="center">---</td>
</tr>
</tr>
</table>
=''S-Type Ellipsoid'' Example b41c385=
<div align="center">
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <th align="center">Figure 1a</th>
   <td align="center" rowspan="4" bgcolor="white">0.28</td>
   <th align="center">Figure 1b</th>
  <td align="center" bgcolor="pink">0.256</td>
  <td align="center" bgcolor="pink">0.80944</td>
  <td align="center" bgcolor="pink">0.03668</td>
  <td align="center">-0.14127</td>
  <td align="center">-0.17453</td>
  <td align="center">-0.03668</td>
  <td align="center">-0.80944</td>
  <td align="center">+3.11750</td>
   <td align="center">-84.992</td>
</tr>
</tr>
<tr>
<tr>
   <td align="left" bgcolor="lightgrey">
   <td align="center" bgcolor="yellow">0.245083</td>
[[File:EFEb41c385.view2.cropped.png|400px|EFE Model b41c385]]
  <td align="center" bgcolor="yellow">0.796512<sup>a</sup></td>
   </td>
  <td align="center" bgcolor="yellow">0.0</td>
   <td align="left" bgcolor="lightgrey">
  <td align="center">0.0</td>
[[File:EFEb41c385.view1.cropped.png|400px|EFE Model b41c385]]
  <td align="center">0.0</td>
   </td>
  <td align="center">0.0</td>
  <td align="center">&hellip;</td>
  <td align="center">&hellip;</td>
  <td align="center"><math>~\infty</math></td>
</tr>
<tr>
  <td align="center" bgcolor="pink">0.231</td>
  <td align="center" bgcolor="pink">0.77651</td>
  <td align="center" bgcolor="pink">- 0.04714</td>
  <td align="center">+0.18156</td>
  <td align="center">+0.23381</td>
  <td align="center">+0.04714</td>
  <td align="center">-0.77651</td>
  <td align="center">+2.99067</td>
   <td align="center">+63.442</td>
</tr>
<tr>
   <td align="center" bgcolor="pink">0.205</td>
  <td align="center" bgcolor="pink">0.72853</td>
  <td align="center" bgcolor="pink">- 0.13511</td>
  <td align="center">+0.52037</td>
  <td align="center">+0.71427</td>
  <td align="center">+0.13511</td>
  <td align="center">-0.72853</td>
  <td align="center">+2.80588</td>
  <td align="center">+20.7674</td>
</tr>
<tr>
  <td align="left" colspan="10">
<sup>a</sup>According to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.
   </td>
</tr>
</tr>
</table>
</table>
</div>




The EFE model that we chose to use in our first successful construction of a COLLADA-based, 3D and interactive animation had the following properties (model selected from the above table):
===Our Parameter Determinations===
<ul>
The parameter values that have been posted above in our Table 1 are typically given with five digits of precision.  This is because, as explained, the values were determined from the ''analytically determined'' values, <math>~\omega_\mathrm{analytic}</math> and <math>~\lambda_\mathrm{analytic}</math>, that were provided by Ou (2006) with only five digit accuracy.  Our Table 2 (shown immediately below) provides values of this same set of model parameters to better than eleven digits accuracy.  We calculated these parameter values by following the steps detailed in earlier subsections of this chapter and, as a foundation, using double-precision versions of ''Numerical Recipes'' algorithms to evaluate the special functions, <math>~F(\phi,k)</math> and <math>~E(\phi,k)</math>.  As an example, the above pair of brief tables titled, ''TEST (part 1)'' and ''TEST (part 2)'' detail all of the intermediate steps that were used in order to determine the high-precision parameter values specifically for the model having the axis-ratio pair <math>~(0.9,0.641)</math>.  This table of higher precision parameter values was primarily generated in order to convince ourselves that we understood from first principles how to accurately determine the properties of Riemann S-type ellipsoids; the lower-precision parameter values that we derived from Ou's work provided a handy means of cross-checking these "first principles" determinations.
  <li><math>~b/a = 0.41</math></li>
  <li><math>~c/a = 0.385</math></li>
  <li><math>~\Omega_\mathrm{EFE} = \omega/\sqrt\pi = 0.971082/\sqrt\pi = 0.547874</math></li>
  <li><math>~\lambda_\mathrm{EFE} = 0.141594/\sqrt\pi = 0.079886</math></li>
</ul>


Figure 1 displays a pair of still-frame images of this (purple) ellipsoidal configuration after the ellipsoid has completed precisely five (counter-clockwise) spin cycles.  (The snapshots have been taken at the same point in time, but from two different "camera" viewing angles.)  The cycle of the "wall mounted" clock is based on the fundamental, EFE-adopted frequency of [&pi; G &rho;]<sup>½</sup>In the left-hand image (labeled Figure 1a),  the time on the clock appears to be about 9:08. This means that as the ellipsoid has completed five spin cycles, the clock has completed approximately [9 + 8/60] &#8776; 9.13 cyclesIn other words, the ratio (ellipsoid-to-clock) of these two frequencies is,
<span id="Table2">In generating our Table 2, we wondered what the approriate ''signs'' were of the various model parameters &#8212; especially when part of our objective is to distinguish between ''direct'' and ''adjunct'' configurationsWe took the following approachFirst we decided that the spin frequency of every ''direct'' configuration should be positive(Evidently, Ou made this same choice.)</span>
<table border="0" cellpadding="5" align="center">


<table border="1" align="center" cellpadding="8" width="90%">
<tr>
<tr>
   <td align="right">
   <td align="center" colspan="10">
<math>~\frac{\Omega_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>
<b>Table 2: &nbsp; Example Riemann S-type Ellipsoids</b> (double-precision evaluation)
   </td>
   </td>
   <td align="center">
</tr>
<math>~\approx</math>
<tr>
   <td align="center" rowspan="2"><math>~\frac{b}{a}</math></td>
  <td align="center" rowspan="2"><math>~\frac{c}{a}</math></td>
  <td align="center" rowspan="1" colspan="4">
Properties of<br /><b>''Direct'' Configurations</b>
   </td>
   </td>
   <td align="left">
   <td align="center" rowspan="1" colspan="4">
<math>~\frac{5}{9.13} = 0.548 \, .</math>
Properties of<br /><b>''Adjoint'' Configurations</b>
   </td>
   </td>
</tr>
</tr>
</table>
This matches the tabulated value of <math>~\Omega_\mathrm{EFE}</math> presented above.  Now, let's examine the motion of an example Lagrangian fluid element, which has been marked in the 3D scene by a red "arrow" riding in the equatorial plane and along the surface of the (purple) ellipsoidal figure.  At time zero, the fluid marker was placed at the end of the longest axis of the ellipsoid that was nearest the "wall clock"; then, as time progressed and the ellipsoidal figure turned counter-clockwise, the fluid marker moved clockwise and completed less than one full "orbit" in the same time that the ellipsoidal figure completed five full spin cycles.  In the right-hand image (labeled Figure 1b), we can see that ''relative'' to the ellipsoidal figure, the fluid marker has moved through approximately three-quarters of its assigned elliptical "orbit"; let's say, 73% of one full cycle.  This means that the ratio of the Lagrangian fluid element's orbital frequency to the frequency of the wall-clock is,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
   <td align="center" rowspan="1"><math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math></td>
<math>~\frac{\lambda_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>
   <td align="center" rowspan="1"><math>~\lambda</math></td>
   </td>
   <td align="center" rowspan="1"><math>~\zeta </math></td>
   <td align="center">
   <td align="center" rowspan="1"><math>~f \equiv \frac{\zeta}{\Omega}</math></td>
<math>~\approx</math>
  <td align="center" rowspan="1"><math>~\omega^\dagger </math></td>
  </td>
  <td align="center" rowspan="1"><math>~\lambda^\dagger </math></td>
   <td align="left">
   <td align="center" rowspan="1"><math>~\zeta^\dagger = \omega^\dagger f^\dagger</math></td>
<math>~\frac{0.73}{9.13} = 0.080 \, .</math>
  <td align="center" rowspan="1"><math>~f^\dagger </math></td>
   </td>
</tr>
</tr>
</table>
This matches the tabulated value of <math>~\lambda_\mathrm{EFE}</math> presented above.
=''Type I Ellipsoid'' Example b1.25c0.470 =
<div align="center">
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <th align="center">Figure 2a</th>
   <td align="center">(1)</td>
   <th align="center">Figure 2b</th>
   <td align="center">(2)</td>
  <td align="center">(3)</td>
  <td align="center">(4)</td>
  <td align="center">(5)</td>
  <td align="center">(6)</td>
  <td align="center">(7)</td>
  <td align="center">(8)</td>
  <td align="center">(9)</td>
  <td align="center">(10)</td>
</tr>
</tr>
<tr>
<tr>
   <td align="left" bgcolor="lightgrey">
   <td align="center" rowspan="7" bgcolor="white">0.90</td>
[[File:TypeI b1.25c470A.png|400px|EFE Model b41c385]]
  <td align="center" bgcolor="pink">0.795</td>
   </td>
  <td align="center" bgcolor="white">+1.147036091720</td>
   <td align="left" bgcolor="lightgrey">
   <td align="center" bgcolor="white">+0.431809451699</td>
[[File:TypeI b1.25c470B.png|400px|EFE Model b41c385]]
   <td align="center">-0.868416786194</td>
   </td>
  <td align="center">-0.757096320116</td>
  <td align="center">-0.431809460593</td>
  <td align="center">-1.147036104571</td>
  <td align="center">+2.306817054749</td>
   <td align="center">-5.342210487323</td>
</tr>
</tr>
</table>
</div>
<span id="Case_I">
We have pulled the parameters for this example ''Type I Ellipsoid'' from Table XIII(a) on p. 170 of EFE; in addition, the ''superior'' values of &beta;<sub>+</sub> and &gamma;<sub>+</sub> have been obtained from eqs. (16) and (17), respectively, as found on p. 131 of Chapter 7, &sect;47.  This model sits along the locus O<sub>2</sub>X<sub>2</sub><sup>(I)</sup> shown in Figure 17 (p. 171) of EFE.</span>
<table border="0" cellpadding="5" align="center">
<tr><td align="left" rowspan="4">
<table border="1" cellpadding="8" align="center">
<tr><th align="center" colspan="2">Example Type I<br />Ellipsoid</th></tr>
<tr>
<tr>
   <td align="center"><math>~\frac{b}{a} = \frac{a_2}{a_1}</math></td>
  <td align="center" bgcolor="pink">0.641</td>
   <td align="center">1.25</td>
  <td align="center" bgcolor="white">+1.131374738327</td>
  <td align="center" bgcolor="white">+0.150771621841</td>
   <td align="center"> -0.303218483925</td>
  <td align="center">-0.268008886644</td>
  <td align="center">-0.150771621877</td>
   <td align="center">-1.131374730590</td>
  <td align="center">+2.275320291519</td>
  <td align="center">-15.091170863305</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\frac{c}{a} = \frac{a_3}{a_1}</math></td>
   <td align="center" bgcolor="pink">0.590</td>
   <td align="center">0.4703</td>
  <td align="center" bgcolor="white">+1.106612583610</td>
</tr>
  <td align="center" bgcolor="white">+0.064060198174</td>
<tr>
   <td align="center">-0.128832176328</td>
   <td align="center"><math>~\Omega_2</math></td>
  <td align="center">-0.116420305902</td>
   <td align="center">0.3639</td>
  <td align="center">-0.064060197762</td>
   <td align="center">-1.106612576964</td>
  <td align="center">+2.225520849228</td>
   <td align="center">-34.741086358509</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\Omega_3</math></td>
   <td align="center" bgcolor="pink">0.564</td>
   <td align="center">0.6633</td>
  <td align="center" bgcolor="white">+1.090339840378</td>
  <td align="center" bgcolor="white">+0.020334563779</td>
  <td align="center">-0.040895067155</td>
  <td align="center">-0.037506716440</td>
   <td align="center">-0.020334563809</td>
  <td align="center">-1.090339837153</td>
  <td align="center">+2.192794561386</td>
  <td align="center">-107.8358300897</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\tan^{-1} \biggl[ \frac{\Omega_3}{\Omega_2} \biggr]</math></td>
   <td align="center" bgcolor="pink">0.538</td>
   <td align="center">61.25&deg;</td>
  <td align="center" bgcolor="white">+1.071485625744</td>
  <td align="center" bgcolor="white">-0.023236834336</td>
  <td align="center">+0.046731855720</td>
  <td align="center">+0.043614077664</td>
  <td align="center">+0.023236835120</td>
  <td align="center">-1.071485656401</td>
  <td align="center">+2.154876708984</td>
   <td align="center">+92.735376233270</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\zeta_2</math></td>
   <td align="center" bgcolor="pink">0.487</td>
   <td align="center">-2.2794</td>
  <td align="center" bgcolor="white">+1.026387311947</td>
  <td align="center" bgcolor="white">-0.108799837242</td>
  <td align="center">+0.218808561563</td>
  <td align="center">+0.213183225210</td>
  <td align="center">+0.108799835209</td>
   <td align="center">-1.026387320039</td>
  <td align="center">+2.064178943634</td>
  <td align="center">+18.972261524065</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\zeta_3</math></td>
   <td align="center" bgcolor="pink">0.333</td>
   <td align="center">-1.9637</td>
  <td align="center" bgcolor="lightgreen">+0.792566980901</td>
  <td align="center" bgcolor="lightgreen">-0.392440787995</td>
  <td align="center">+0.789242029190</td>
  <td align="center">+0.995804846843</td>
  <td align="center">+0.392440793882</td>
   <td align="center">-0.792566979129</td>
  <td align="center">+1.593940258026</td>
  <td align="center">+4.061606964516</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\tan^{-1} \biggl[ \frac{\zeta_3}{\zeta_2} \biggr]</math></td>
   <td align="center" rowspan="1" bgcolor="white">0.74</td>
   <td align="center">40.74&deg;</td>
  <td align="center" bgcolor="pink">0.692</td>
  <td align="center" bgcolor="lightgreen">+1.132148956838</td>
  <td align="center" bgcolor="lightgreen">+0.385991660900</td>
  <td align="center">-0.807244181633</td>
  <td align="center">-0.713019398562</td>
  <td align="center">-0.385991654519</td>
  <td align="center">-1.132148989537</td>
  <td align="center">2.367721319199</td>
   <td align="center">-6.134125500116</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\beta_+</math></td>
   <td align="center" rowspan="2" bgcolor="white">0.41</td>
   <td align="center">1.13449 (1.13332)</td>
  <td align="center" bgcolor="pink">0.385</td>
  <td align="center" bgcolor="lightgreen">+0.971082162758</td>
  <td align="center" bgcolor="lightgreen">+0.141593941719</td>
   <td align="center">-0.403404593468</td>
  <td align="center">-0.415417564427</td>
  <td align="center">-0.141593939418</td>
  <td align="center">-0.971082191477</td>
  <td align="center">2.766636848450</td>
  <td align="center">-19.539231537777</td>
</tr>
</tr>
<tr>
<tr>
   <td align="center"><math>~\gamma_+</math></td>
   <td align="center" bgcolor="pink">0.333</td>
   <td align="center">1.8052</td>
  <td align="center" bgcolor="white">+0.929630138695</td>
</tr>
  <td align="center" bgcolor="white">+0.003311666790</td>
</table>
   <td align="center">-0.009435019456</td>
</td>
  <td align="center">-0.010149218281</td>
<th align="center">EFE Table XIII (p. 170)</th>
  <td align="center">-0.003311666699</td>
  <td align="center">-0.929630099681</td>
  <td align="center">+2.648538827896</td>
  <td align="center">-799.7601146950</td>
</tr>
</tr>
<tr>
<tr>
<td align="right">
  <td align="center" rowspan="4" bgcolor="white">0.28</td>
[[File:EFE TableXIIIp170.cropped.png|500px|EFE Table XIII (p. 170)]]
  <td align="center" bgcolor="pink">0.256</td>
</td>
  <td align="center" bgcolor="lightgreen">+0.809436834686</td>
</tr>
  <td align="center" bgcolor="lightgreen">+0.036676037913</td>
<tr>
  <td align="center">-0.141255140305</td>
<th align="center">EFE Figure 17 (p. 171)</th>
  <td align="center">-0.174510396110</td>
  <td align="center">-0.036676038521</td>
  <td align="center">-0.809436833116</td>
  <td align="center">+3.117488145828</td>
  <td align="center">-85.000678306244</td>
</tr>
</tr>
<tr>
<tr>
<td align="right">[[File:EFE Fig17p171.cropped.png|500px|EFE Figure 17 (p. 171)]]</td>
  <td align="center" bgcolor="yellow">0.245083</td>
  <td align="center" bgcolor="white">0.796512<sup>a</sup></td>
  <td align="center" bgcolor="white">0.0</td>
  <td align="center">0.0</td>
  <td align="center">0.0</td>
  <td align="center">0.0</td>
  <td align="center">&hellip;</td>
  <td align="center">&hellip;</td>
  <td align="center"><math>~\infty</math></td>
</tr>
</tr>
</table>
<span id="explanation">In explaining the elements</span> depicted in Figure 2 we will reference two separate cartesian frames:  The (inertial) "lab" frame and a "body" frame affixed to the ellipsoid.  The x-y plane of the inertial frame is identified by the square, grey/black frame and its z-axis is identified by a thin, green, pointed vertical stick.  As depicted in both panels of Figure 2, the x-axis of the ellipsoid's body frame aligns with the x-axis of the inertial frame; in panel 2a, we're generally looking in the plus-x direction toward the clock, and in both panels a black arrow "tip" is affixed to the ellipsoid's negative x-axis.  In this "Type I" ellipsoid &#8212; as opposed to the "S-Type" ellipsoids discussed earlier &#8212; the x-axis of the body frame aligns permanently with the ''intermediate'' axis of the (purple) ellipsoidal configuration; following EFE, we assign the value, a = 1, to this intermediate length.  The body frame's y-axis is permanently aligned with the configurations's longest axis; in the particular model displayed in Figure 2, b/a = 1.25.  And the body frame's z-axis is permanently aligned with the configuration's shortest axis; in this case, c/a = 0.470.
In ''S-Type'' ellipsoids (discussed previously), the ellipsoidal configuration spins about its shortest axis &#8212; this means that the ellipsoidal configuration's angular velocity vector has no component along either the x-axis or the y-axis (&Omega;<sub>2</sub> = &Omega;<sub>1</sub> = 0).  But for the ''Type I'' ellipsoid shown in Figure 2, &Omega;<sub>2</sub> = 0.3639 while &Omega;<sub>3</sub> = 0.6633.  This means that the configuration's spin axis &#8212; associated with the inertial frame's z-axis (the green pointed stick in both panels of Figure 2) &#8212; is ''not'' aligned with the z-axis of the (purple) ellipsoidal configuration.  As is illustrated best in panel 2a, the ellipsoidal configuration is tipped ''about the x-axis'' (&Omega;<sub>1</sub> = 0) by an angle, 61.25&deg; = tan<sup>-1</sup>(&Omega;<sub>3</sub>/&Omega;<sub>2</sub>) to the spin axis.  When this COLLADA-based 3D scene is animated, the purple ellipsoid spins about the z-axis (green pointed stick) of the inertial frame at a frequency, |&Omega;| = [&Omega;<sub>2</sub><sup>2</sup> + &Omega;<sub>3</sub><sup>2</sup>]<sup>&frac12;</sup> = 0.7566, in units of [&pi; G &rho;]<sup>&frac12;</sup>.
<table border="1" width="80%" align="center" cellpadding="10">
<tr>
<tr>
<td align="left">
  <td align="center" bgcolor="pink">0.231</td>
In our COLLADA-based animation, we associate TIME=4 with one clock cycle. Given that <math>~|\Omega| = 0.7566 [\pi G \rho]^{1 / 2}</math> for this particular example Type I Riemann ellipsoid, we recognize that the number of clock cycles required to complete one spin about the green axis is <math>~1.0/0.7566 = 1.3217</math> cycles.  Hence spinning through 360&deg; is equivalent to TIME = 5.2868; or, TIME = 4 is equivalent to a spin angle of 272.38&deg;.
  <td align="center" bgcolor="white">+0.776514825339</td>
</td>
  <td align="center" bgcolor="white">-0.047142035397</td>
  <td align="center">+0.181564182043</td>
  <td align="center">+0.233819345828</td>
  <td align="center">+0.047142037070</td>
  <td align="center">-0.776514835457</td>
  <td align="center">+2.990691423416</td>
  <td align="center">+63.440011724689</td>
</tr>
</tr>
</table>
<tr>
  <td align="center" bgcolor="pink">0.205</td>
  <td align="center" bgcolor="white">+0.728526018042</td>
  <td align="center" bgcolor="white">-0.135108121071</td>
  <td align="center">+0.520359277725</td>
  <td align="center">+0.714263156392</td>
  <td align="center">+0.135108125079</td>
  <td align="center">-0.728526039364</td>
  <td align="center">+2.805866003036</td>
  <td align="center">+20.767558718483</td>
</tr>
<tr>
  <td align="left" colspan="10">
<sup>a</sup>According to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.
  </td>
</tr>
</table>


<span id="EFEvelocities">Now &#8230; how do we determine the motion of Lagrangian fluid elements due to the nonzero internal vorticity of the ellipsoidal structure?  Evidently the vorticity vector is tipped at an angle of 40.74&deg; = tan<sup>-1</sup>(&zeta;<sub>3</sub>/&zeta;<sub>2</sub>) to the inertial frame's z-axis.  <b><font color="red">[The preceding sentence is incorrect!  This is a misinterpretation of how the "tipping angle" is determined.  The correct expression for this "tipping angle" is [[#Tipped|presented below]].]</font></b> This presumably means that, as viewed from the frame of reference of the spinning ellipsoidal figure, each Lagrangian fluid element moves along a closed (approximately elliptical?) path in a plane that is perpendicular to this vorticity vector. How we determine these various trajectories precisely?  </span>
<span id="Fig2">&nbsp;</span>
<table border="1" cellpadding="5" width="90%" align="center">
<tr><td align="center" colspan="1">'''Figure 2: &nbsp;EFE Diagram'''</td>
<td align="left" rowspan="2">
In the context of our broad discussion of ellipsoidal figures of equilibrium, the label "EFE Diagram" refers to a two-dimensional parameter space defined by the pair of axis ratios (b/a, c/a), ''usually'' covering the ranges, 0 &le; b/a &le; 1 and 0 &le; c/a &le; 1.  The classic/original version of this diagram appears as Figure 2 on p. 902 of [http://adsabs.harvard.edu/abs/1965ApJ...142..890C S. Chandrasekhar (1965, ApJ, vol. 142, pp. 890-921)]; a somewhat less cluttered version appears on p. 147 of Chandrasekhar's [<b>[[User:Tohline/Appendix/References#EFE|<font color="red">EFE</font>]]</b>].


The version of the EFE Diagram shown here, on the left, highlights four model ''sequences'', all of which also can be found in the original version:
<ul>
<ul>
<li>First, we acknowledge that EFE provides an expression for the velocity vector of each fluid element, given its instantaneous ''body''-coordinate position (x, y, z) = (x<sub>1</sub>, x<sub>2</sub>, x<sub>3</sub>). Namely &#8212; see eq. 154 of Chapter 7, &sect;51 (p. 156) &#8212;
<li>''Jacobi'' sequence &#8212; the smooth curve that runs through the set of small, dark-blue, diamond-shaped markers; the data identifying the location of these markers have been drawn from &sect;39, Table IV of [<b>[[User:Tohline/Appendix/References#EFE|<font color="red">EFE</font>]]</b>].  The small red circular markers lie along this same sequence; their locations are taken from our own determinations, as detailed in [[User:Tohline/ThreeDimensionalConfigurations/JacobiEllipsoids#Table2|Table 2]] of our accompanying discussion of Jacobi ellipsoids. All of the models along this sequence have <math>~f \equiv \zeta/\Omega_f = 0</math> and are therefore solid-body rotators, that is, there is no internal motion when the configuration is viewed from a frame that is rotating with frequency, <math>~\Omega_f</math>.</li>
<table border="0" cellpadding="5" align="center">
<li>''Dedekind'' sequence &#8212; a smooth curve that lies precisely on top of the ''Jacobi'' sequence. Each configuration along this sequence is ''adjoint'' to a model on the ''Jacobi'' sequence that shares its (b/a, c/a) axis-ratio pair.  All ellipsoidal figures along this sequence have <math>~1/f = \Omega_f/\zeta = 0</math> and are therefore stationary as viewed from the ''inertial'' frame; the angular momentum of each configuration is stored in its internal motion (vorticity).</li>
<li>The X = -1 ''self-adjoint'' sequence &#8212; At every point along this sequence, the value of the key frequency ratio, <math>~\zeta/\Omega_f</math>, in the ''adjoint'' configuration <math>~(f_+)</math> is identical to the value of the frequency ratio in the ''direct'' configuration  <math>~(f_-)</math>; specifically, <math>~f_+ = f_- = -(a^2+b^2)/(ab)</math>.  The data identifying the location of the small, solid-black markers along this sequence have been drawn from &sect;48, Table VI of [<b>[[User:Tohline/Appendix/References#EFE|<font color="red">EFE</font>]]</b>].</li>
<li>The X = +1 ''self-adjoint'' sequence &#8212; At every point along this sequence, the value of the key frequency ratio, <math>~\zeta/\Omega_f</math>, in the ''adjoint'' configuration <math>~(f_+)</math> is identical to the value of the frequency ratio in the ''direct'' configuration  <math>~(f_-)</math>; specifically, <math>~f_+ = f_- = +(a^2+b^2)/(ab)</math>The data identifying the location of the small, solid-black markers along this sequence have been drawn from &sect;48, Table VI of [<b>[[User:Tohline/Appendix/References#EFE|<font color="red">EFE</font>]]</b>].</li>
</ul>


Riemann S-type ellipsoids all lie between or on the two (self-adjoint) curves marked "X = -1" and "X = +1" in the EFE Diagram.  The yellow circular markers in the diagram shown here, on the left, identify four Riemann S-type ellipsoids that were examined by [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)] and that we have also chosen to use as examples.
</td>
</tr>
<tr>
<tr>
  <td align="right">
<td align="left">
<math>~u_1</math>
[[File:EFEdiagram4.png|left|500px|EFE Diagram identifying example models from Ou (2006)]]
  </td>
</td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 y + \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 z</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~+\biggl[ \frac{a^2}{ b^2} \biggr]\Omega_3 \gamma  y - \biggl[ \frac{a^2}{c^2} \biggr] \Omega_2 \beta  z \, ,</math>
  </td>
</tr>
</tr>
</table>


=Feeding a 3D Animation=
==Initial Thoughts==
Let's examine the elliptical trajectory of a Lagrangian particle that is moving in the equatorial plane of a Riemann S-Type ellipsoid. As viewed in a frame that is spinning about the Z-axis at angular frequency, <math>~\Omega</math>, the trajectory is defined by,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~u_2</math>
<math>
r^2
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
<math>
~=
</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~+\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 x</math>
<math>~
  </td>
\biggl(\frac{x}{a} \biggr)^2 + \biggl(\frac{y}{b}\biggr)^2 \, ,
  <td align="center">
</math>
<math>~=</math>
  </td>
  <td align="left">
<math>~- \Omega_3 \gamma  x \, ,</math>
   </td>
   </td>
</tr>
</tr>


</table>
where <math>~0 < r \le 1</math>.  (The surface of the relevant ellipsoid is associated with the value, <math>~r=1</math>.)
Let's choose a pair of axis ratios &#8212; for example, <math>~b/a = 0.28</math> and <math>~c/a = 0.231</math> &#8212; then, from Table 1 of our [[#Models_Examined_by_Ou_.282006.29|above discussion]], draw the associated value of either <math>~\lambda</math> or <math>~\zeta</math> that corresponds to the Jacobi-like equilibrium configuration &#8212; in this example, <math>~\lambda = -0.04714</math> and <math>~\zeta = +0.18156</math>.  Then, for any point <math>~(x,y)</math> inside of the ellipsoid, the fluid's velocity components (as viewed from the rotating frame of reference) are,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~u_3</math>
<math>
v_x  = \frac{dx}{dt}  = \lambda \biggl( \frac{ay}{b} \biggr) = -0.16836 ~y
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 x</math>
<math>~
  </td>
v_y  = \frac{dy}{dt}  = - \lambda \biggl( \frac{bx}{a} \biggr) = + 0.01320~x \, .
  <td align="center">
</math>
<math>~=</math>
  </td>
  <td align="left">
<math>~-\Omega_2 \beta  x \, .</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
But we cannot immediately deduce, from these expressions alone, what the time-dependent behavior is of the three Lagrangian coordinates (x, y, z).
</li>
<li>
Second, we need to determine how to mathematically specify, then display, the coordinates of a plane that is tipped about the x-axis at an arbitrary angle to the equatorial plane of the (purple) ellipsoidal figure.
</li>
</ul>


<span id="TippedPlane">Regarding the second issue, let's identify the coordinates of a closed curve (an ellipse?) that identifies the the intersection between a "tipped" plane and the ''surface'' of the underlying ellipsoid.  The surface of the ellipsoid is defined by the equation,</span>
Alternatively, we have,
<table border="0" cellpadding="5" align="center">


<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~1</math>
<math>
u_x = \frac{dx}{dt} = Q_1  y = - \biggl[ 1 + \frac{b^2}{a^2} \biggr]^{-1}\zeta ~y = -0.16836 ~y
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\biggl( \frac{x}{a} \biggr)^2 + \biggl( \frac{y}{b} \biggr)^2 + \biggl( \frac{z}{c} \biggr)^2 \, .</math>
<math>~
u_y  = \frac{dy}{dt}= Q_2 x  = + \biggl[ 1 + \frac{a^2}{b^2} \biggr]^{-1}\zeta ~x = + 0.01320~x \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
And the "tipped" plane is defined such that, for any/all values of x,
<table border="0" cellpadding="5" align="center">


Now, each Lagrangian fluid element's motion is oscillatory in both the <math>~x</math> and <math>~y</math> coordinate directions.  So let's see how this plays out.  Suppose,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~z </math>
<math>
x = x_\mathrm{max} \cos(\varphi t)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~my + z_0 \, .</math>
<math>~
y = y_\mathrm{max} \sin(\varphi t) \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
This means,
<table border="0" cellpadding="5" align="center">


Then,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~1</math>
<math>
\frac{dx}{dt} = -  x_\mathrm{max}\varphi \sin(\varphi t) = -  \biggl( \frac{x_\mathrm{max}}{y_\mathrm{max}}\biggr) \varphi y = - \varphi \biggl(\frac{ay}{b}\biggr)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\biggl( \frac{x}{a} \biggr)^2 + \frac{1}{b^2}\biggl( \frac{z-z_0}{m} \biggr)^2 + \biggl( \frac{z}{c} \biggr)^2 </math>
<math>~
\frac{dy}{dt} = y_\mathrm{max} \varphi \cos(\varphi t) = + \biggl( \frac{y_\mathrm{max}}{x_\mathrm{max}}\biggr) \varphi x = + \varphi \biggl(\frac{bx}{a}\biggr) \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>


Hence our functional representation of the time-dependent behavior of both <math>~x</math> and <math>~y</math> works perfectly if, for each orbit inside of or on the surface of the configuration, we set <math>~\varphi = - \lambda</math> and if the ratio <math>~y_\mathrm{max}/x_\mathrm{max} = (b/a)</math>.  Hooray!
==Preferred Normalizations==
Let's do this again, assuming that <math>~x</math> and <math>~y</math> both have units of length and that <math>~t</math> has the unit of time.  Then, let's use <math>~a</math> to normalize lengths and use <math>~(\pi G \rho)^{-1 / 2}</math> to normalize time. We therefore have,
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\Rightarrow ~~~\biggl( \frac{x}{a} \biggr)^2</math>
<math>
\frac{x}{a} = \biggl(\frac{ x_\mathrm{max} }{a}\biggr) \cos\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}}  \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr]
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~1 - \biggl(\frac{z_0}{mb}\biggr)^2 \biggl( \frac{z}{z_0} - 1 \biggr)^2 - \biggl( \frac{z}{c} \biggr)^2 \, .</math>
<math>~
\frac{y}{a} = \biggl(\frac{ y_\mathrm{max} }{a}\biggr) \sin\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}}  \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr] \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
If we specifically set m = 1 &#8212; that is, choose a slope of 45&deg; &#8212; and set z<sub>0</sub> = c &#8212; that is, choose a plane that intersects the north pole of the (purple) ellipsoid &#8212; we then have,
 
<table border="0" cellpadding="5" align="center">
 
<table border="1" cellpadding="10" width="80%" align="center"><tr><td align="left">
<font color="red">'''NOTE:'''</font> &nbsp; When implementing in an xml-based COLLADA (3D animation) file, we associate <math>~\mathrm{TIME} = 4</math> with <math>~t \cdot (\pi G \rho)^{1 / 2} = 2\pi</math>.  Hence we can everywhere replace <math>~t \cdot (\pi G \rho)^{1 / 2}</math> with (in ''radians'') <math>~(\pi/2)\cdot \mathrm{TIME}</math> or (in ''degrees'') <math>~90 \cdot \mathrm{TIME}</math>.
 
<br />
This also means that, if <math>~\varphi/(\pi G \rho)^{1 / 2} = 1</math>,  each Lagrangian fluid element will move through one complete orbit (as viewed from a frame that is rotating with the ellipsoidal figure) in the time it takes the hand of the wall-mounted clock to complete one cycle.
</td></tr></table>
 
Next, let's normalize the velocities such that <math>~\rho</math> and the total mass, <math>~M</math>, are both assumed to be the same in every examined Riemann ellipsoid.  In particular, we will normalize to,
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\frac{x}{a} </math>
<math>~v_0</math>
  </td>
  <td align="center">
<math>~\equiv</math>
  </td>
  <td align="left">
<math>~(abc)^{1 / 3}(\pi G \rho)^{1 / 2}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 1,502: Line 1,983:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\pm \biggl[ 1 - \biggl(\frac{c}{b}\biggr)^2 \biggl( \frac{z}{c} - 1 \biggr)^2 - \biggl( \frac{z}{c} \biggr)^2 \biggr]^{1 / 2} \, .</math>
<math>~a(\pi G \rho)^{1 / 2} \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{1 / 3} \, ,</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
<b><font color="red">[In retrospect, we acknowledge that this was a useful way to explore how to determine the shape of each Lagrangian-fluid-element orbit. It is important to emphasize, however, that our choice of a 45&deg; tip angle was only meant to provide an example test calculation.  Eventually (see [[#Tipped|below]]) we determined that, for this particular Type I example, the correct tipping angle is -19.02&deg;.]</font></b>  Remembering that for the chosen ellipsoidal model (a, b, c) = (1.000, 1.250, 0.4703), the following table identifies the coordinates of a collection of points that simultaneously lie on the surface of the ellipsoid and within the chosen 45&deg; "tipped" plane.  These points are each represented by a small yellow cube in both panels of Figure 2.
in which case we have,


<table border="1" cellpadding="8" align="center">
<table align="center" border=0 cellpadding="3">
<tr>
<tr>
   <th align="center" colspan="3">m = 1  and z_0 = c</th>
   <td align="right">
<math>
\frac{1}{v_0} \cdot \frac{dx}{dt} =  - \frac{\varphi}{(\pi G \rho)^{1 / 2} } \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr)
</math>
  </td>
  <td align="center">
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
  </td>
  <td align="left">
<math>~
\frac{1}{v_0} \cdot \frac{dy}{dt} = + \frac{\varphi}{(\pi G \rho)^{1 / 2} } \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{x}{a}\biggr) \, .
</math>
  </td>
</tr>
</tr>
<tr>
  <th align="center">z</th>
  <th align="center">y</th>
  <th align="center">|x|</th>
</tr>
<tr>  <td align="center">c</td>  <td align="center">0</td>  <td align="center">0</td> </tr>
<tr>  <td align="center">0.8c</td>  <td align="center">-0.2c</td>  <td align="center">0.5953</td> </tr>
<tr>  <td align="center">0.5c</td>  <td align="center">-0.5c</td>  <td align="center">0.8454</td> </tr>
<tr>  <td align="center">0.25c</td>  <td align="center">-0.75c</td>  <td align="center">0.9262</td> </tr>
<tr>  <td align="center">0</td>  <td align="center">-c</td>  <td align="center">0.9265</td> </tr>
<tr>  <td align="center">-0.25c</td>  <td align="center">-1.25c</td>  <td align="center">0.8464</td> </tr>
<tr>  <td align="center">-0.5c</td>  <td align="center">-1.5c</td>  <td align="center">0.6569</td> </tr>
<tr>  <td align="center">-0.75227c</td>  <td align="center">-1.75227c</td>  <td align="center">0</td> </tr>
</table>
</table>
Finally, setting, <math>~\varphi/(\pi G\rho)^{1 / 2} \rightarrow -\lambda_\mathrm{EFE}</math> means,


 
<table align="center" border=0 cellpadding="3">
Here are a few thoughts/possible lines-of-attack to consider when addressing the first issue stated above.
<ol type="A">
<li>
It is likely that the angle at which the plane of motion is tilted about the x-axis of the "body" frame is directly related to the ratio, <math>~\zeta_3/\zeta_2</math>.
</li>
<li>
It is likely that the angle at which the plane of motion is tilted with respect to the z-axis of the "body" frame can be deduced by considering the ratio of the velocity components, v<sub>y</sub> and v<sub>z</sub>, when the x-component of the velocity vector is known to be zero; that is, when the fluid element is "crossing the x-axis."
</li>
<li>
Does the closed-orbit motion '''in''' the tipped plane always form a (off-center) ellipse?
</li>
<li>
Once you know the exact angle at which the orbital plane is tipped about the x-axis, an Euler-angle projection of every fluid particle's velocity vector should reduce to in-the-plane motion that has only two components.  Once this transformation is made &#8212; especially if the resulting orbit is always a closed ellipse &#8212; we should be able to determine analytic expressions for the time-dependent behavior of each fluid element's x and y coordinate positions in the orbit plane and, subsequently, the (x, y, z) coordinate positions in the "body" frame.
</li>
</ol>
 
==Regarding thought "A"==
 
For the example model depicted in Figure 2, we have,
<table border="0" cellpadding="5" align="center">
 
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~\theta_\mathrm{tip} \equiv \tan^{-1}\biggl( \frac{\zeta_3}{\zeta_2} \biggr)</math>
<math>
V_x \equiv \frac{1}{v_0} \cdot \frac{dx}{dt} =  \lambda_\mathrm{EFE} \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\tan^{-1}\biggl( \frac{1.9637}{2.2794} \biggr) = 40.74^{\circ}</math>
<math>~
V_y \equiv \frac{1}{v_0} \cdot \frac{dy}{dt} = - \lambda_\mathrm{EFE} \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3}  \cdot \biggl(\frac{x}{a}\biggr) \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>


==Example Mach Surface==


==Regarding thought "B"==
Let's try to plot the "Mach surface" for the example model, b41c385, referenced below.  Its relevant parameter values are,
When a fluid element crosses the x-axis we should expect z = 0. <b><font color="red">This needs to be rethought because the center of the closed elliptical trajectory of most fluid elements will be offset from the body's inherent z-axis.</font></b>
<ul>
 
  <li><math>~b/a = 0.41</math></li>
==Regarding thought "D"==
  <li><math>~c/a = 0.385</math></li>
<table border="0" cellpadding="5" align="center">
  <li><math>~\lambda_\mathrm{EFE} = 0.079886</math></li>
</ul>
Hence, if we set a = 1 then we have,


<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
   <td align="right"><math>~V_x</math></td>
<math>~v_x\biggr|_\mathrm{tip}</math>
  <td align="center"><math>=</math></td>
   </td>
  <td align="left"><math>~(0.079886) \biggl(\frac{1}{0.41}\biggr)\biggl( 1.85034 \biggr) \cdot y</math></td>
   <td align="center">
   <td align="center">&nbsp; &nbsp; &nbsp;and&nbsp; &nbsp; &nbsp;</td>
<math>~=</math>
   <td align="right"><math>~V_y</math></td>
   </td>
   <td align="center"><math>=</math></td>
   <td align="left">
   <td align="left"><math>~- (0.079886)  \biggl(0.41\biggr) \biggl( 1.85034 \biggr)  \cdot x</math></td>
<math>~v_x\biggr|_\mathrm{body}</math>
</tr>
   </td>
<tr>
  <td align="right">&nbsp;</td>
  <td align="center"><math>=</math></td>
  <td align="left"><math>~0.3605 y</math></td>
  <td align="center">&nbsp; </td>
  <td align="right">&nbsp;</td>
  <td align="center"><math>=</math></td>
   <td align="left"><math>~- 0.0606 x</math></td>
</tr>
</tr>
</table>


Borrowing from an [[User:Tohline/Appendix/Ramblings/RiemannB74C692#location_X|accompanying discussion]], we have the following example data set.
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <td align="right">
   <th align="center" colspan="11">''Direct''</th>
<math>~v_y\biggr|_\mathrm{tip}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~v_y|_\mathrm{body}\cdot \cos\theta + v_z|_\mathrm{body}\cdot \sin\theta</math>
  </td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
   <td align="center" rowspan="2">n</td>
<math>~v_z\biggr|_\mathrm{tip}</math>
   <td align="center" colspan="2">Axisymmetric</td>
   </td>
   <td align="center" colspan="1">b41c385</td>
   <td align="center">
   <td align="center" colspan="3" bgcolor="lightblue">Surface</td>
<math>~=</math>
   <td align="center" colspan="3">|V| = 0.1</td>
   </td>
   <td align="left">
<math>~-v_y|_\mathrm{body}\cdot \sin\theta + v_z|_\mathrm{body}\cdot \cos\theta</math>
  </td>
</tr>
</tr>
</table>
Setting <math>~v_z\biggr|_\mathrm{tip} = 0</math> implies,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
   <td align="center">x<sub>0</sub></td>
<math>~v_y|_\mathrm{body}\cdot \sin\theta </math>
  <td align="center">y<sub>0</sub></td>
   </td>
   <td align="center">y = 0.41 &times; y<sub>0</sub></td>
   <td align="center">
   <td align="center">V<sub>x</sub></td>
<math>~=</math>
  <td align="center">V<sub>y</sub></td>
   </td>
   <td align="center">|V|</td>
   <td align="left">
   <td align="center">''factor''</td>
<math>~v_z|_\mathrm{body}\cdot \cos\theta</math>
  <td align="center">x</td>
   </td>
   <td align="center">y</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">1</td>
<math>~\Rightarrow ~~~ \tan\theta </math>
   <td align="right">1.0000</td>
   </td>
  <td align="right">0.0000</td>
   <td align="center">
   <td align="right">0.0000</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">0.0000</td>
   </td>
  <td align="right">-0.0606</td>
   <td align="left">
   <td align="right">0.0606</td>
<math>~\biggl(\frac{v_z}{v_y}\biggr)_\mathrm{body}</math>
   <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">2</td>
&nbsp;
   <td align="right">0.9921</td>
   </td>
  <td align="right">-0.1253</td>
   <td align="center">
   <td align="right">-0.0514</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.0185</td>
   </td>
  <td align="right">-0.0601</td>
   <td align="left">
   <td align="right">0.0629</td>
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \biggl[ \frac{b^2}{a^2 + b^2} \biggr]^{-1} \zeta_3^{-1}</math>
   <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">3</td>
&nbsp;
   <td align="right">0.9686</td>
   </td>
  <td align="right">-0.2487</td>
   <td align="center">
   <td align="right">-0.1020</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.0368</td>
   </td>
  <td align="right">-0.0587</td>
   <td align="left">
   <td align="right">0.0693</td>
<math>~- \frac{\zeta_2}{\zeta_3}\biggl[ \frac{(c/a)^2}{1 + (c/a)^2} \biggr] \biggl[ \frac{(b/a)^2}{1 + (b/a)^2} \biggr]^{-1} \, .</math>
   <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
</table>
For our particular example, then,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
  <td align="center">4</td>
<math>~\tan\theta</math>
   <td align="right">0.9298</td>
   </td>
  <td align="right">-0.3681</td>
   <td align="center">
   <td align="right">-0.1509</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.0544</td>
   </td>
  <td align="right">-0.0563</td>
   <td align="left">
   <td align="right">0.0783</td>
<math>~- \frac{2.2794}{1.9637}\biggl[ \frac{(0.4703)^2}{1 + (0.4703)^2} \biggr] \biggl[ \frac{(1.25)^2}{1 + (1.25)^2} \biggr]^{-1} </math>
   <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
   <td align="center">5</td>
&nbsp;
   <td align="right">0.8763</td>
  </td>
  <td align="right">-0.4818</td>
   <td align="center">
   <td align="right">-0.1975</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.0712</td>
   </td>
  <td align="right">-0.0531</td>
   <td align="left">
  <td align="right">0.0888</td>
<math>~- \frac{2.2794}{1.9637}\biggl[ \frac{(0.4703)^2}{1 + (0.4703)^2} \biggr] \biggl[ \frac{(1.25)^2}{1 + (1.25)^2} \biggr]^{-1} = - 0.3448</math>
  <td align="center">---</td>
   </td>
  <td align="center">---</td>
   <td align="center">---</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
   <td align="center">6</td>
<math>~\Rightarrow ~~~ \theta</math>
  <td align="right">0.8090</td>
   </td>
   <td align="right">-0.5878</td>
   <td align="center">
   <td align="right">-0.2410</td>
<math>~=</math>
  <td align="right" bgcolor="lightblue">-0.0869</td>
   </td>
   <td align="right">-0.0490</td>
   <td align="left">
   <td align="right">0.0998</td>
<math>~\tan^{-1}(-0.3448) = - 19.0^{\circ} \, . </math>
  <td align="center">1.002</td>
   </td>
  <td align="center">0.8090</td>
   <td align="center">-0.2410</td>
</tr>
</tr>
</table>
Now, given that,
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
  <td align="center">7</td>
<math>~x</math>
   <td align="right">0.7290</td>
   </td>
  <td align="right">-0.6845</td>
   <td align="center">
   <td align="right">-0.2807</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1012</td>
   </td>
  <td align="right">-0.0442</td>
   <td align="left">
   <td align="right">0.1104</td>
<math>~x_t \, ,</math>
   <td align="center">0.9058</td>
   </td>
  <td align="center">0.6603</td>
   <td align="center">-0.2543</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">8</td>
<math>~y</math>
   <td align="right">0.6374</td>
   </td>
  <td align="right">-0.7705</td>
   <td align="center">
   <td align="right">-0.3159</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1139</td>
   </td>
  <td align="right">-0.0386</td>
   <td align="left">
   <td align="right">0.1203</td>
<math>~y_t \cos\theta - z_t \sin\theta \, ,</math>
   <td align="center">0.8313</td>
   </td>
  <td align="center">0.5298</td>
   <td align="center">-0.2626</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">9</td>
<math>~z</math>
   <td align="right">0.5358</td>
   </td>
  <td align="right">-0.8443</td>
   <td align="center">
   <td align="right">-0.3462</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1248</td>
   </td>
  <td align="right">-0.0325</td>
   <td align="left">
   <td align="right">0.1290</td>
<math>~z_t \cos\theta + y_t \sin\theta \, ,</math>
   <td align="center">0.7752</td>
   </td>
  <td align="center">0.4153</td>
   <td align="center">-0.2684</td>
</tr>
</tr>
</table>
we can generate the following expressions for the fluid velocity components ''in'' the tipped plane:
<table border="0" cellpadding="5" align="center">
<tr>
<tr>
   <td align="right">
  <td align="center">10</td>
<math>~v_z\biggr|_\mathrm{tip}</math>
   <td align="right">0.4258</td>
   </td>
  <td align="right">-0.9048</td>
   <td align="center">
   <td align="right">-0.3710</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1337</td>
   </td>
  <td align="right">-0.0258</td>
   <td align="left">
   <td align="right">0.1362</td>
<math>~0\, ,</math>
   <td align="center">0.7342</td>
   </td>
  <td align="center">0.3126</td>
   <td align="center">-0.2724</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">11</td>
<math>~v_x\biggr|_\mathrm{tip}</math>
   <td align="right">0.3090</td>
   </td>
  <td align="right">-0.9511</td>
   <td align="center">
   <td align="right">-0.3899</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1406</td>
   </td>
  <td align="right">-0.0187</td>
   <td align="left">
   <td align="right">0.1418</td>
<math>~v_x\biggr|_\mathrm{body}</math>
   <td align="center">0.7052</td>
   </td>
  <td align="center">0.2179</td>
   <td align="center">-0.2750</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">12</td>
&nbsp;
   <td align="right">0.1874</td>
   </td>
  <td align="right">-0.9823</td>
   <td align="center">
   <td align="right">-0.4027</td>
<math>~=</math>
   <td align="right" bgcolor="lightblue">-0.1452</td>
   </td>
  <td align="right">-0.0114</td>
   <td align="left">
   <td align="right">0.1456</td>
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 y + \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 z</math>
   <td align="center">0.6868</td>
   </td>
  <td align="center">0.1287</td>
   <td align="center">-0.2766</td>
</tr>
</tr>
<tr>
<tr>
   <td align="right">
  <td align="center">13</td>
&nbsp;
  <td align="right">0.0628</td>
  <td align="right">-0.9980</td>
  <td align="right">-0.4092</td>
  <td align="right" bgcolor="lightblue">-0.1475</td>
  <td align="right">-0.0038</td>
  <td align="right">0.1476</td>
  <td align="center">0.6775</td>
  <td align="center">0.0425</td>
  <td align="center">-0.2772</td>
</tr>
</table>
 
 
In an [[User:Tohline/Apps/MaclaurinSpheroids#Equilibrium_Structure|accompanying discussion]] of axisymmetric configurations, we have recognized that, at any point inside the configuration, the square of the sound speed is given approximately by the enthalpy where,
<table border="0" cellpadding="5" align="center">
 
<tr>
   <td align="right">
<math>~
c^2 \sim H(x, y, z)
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 1,784: Line 2,252:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \biggl[ y_t \cos\theta - z_t \sin\theta \biggr] + \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl[ z_t \cos\theta + y_t \sin\theta \biggr]</math>
<math>~\frac{P(x, y, z)}{\rho} =
C_B - \Phi_\mathrm{eff}(x, y, z)
</math>
   </td>
   </td>
</tr>
</tr>
Line 1,797: Line 2,267:
   <td align="left">
   <td align="left">
<math>~
<math>~
y_t \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
C_B - \biggl[
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
\Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)
+ z_t\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \sin\theta
- \frac{1}{2} \lambda^2(x^2 + y^2
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \cos\theta \biggr\} \, ,
+ \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr)  
\biggr]
</math>
</math>
   </td>
   </td>
Line 1,807: Line 2,278:
<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~v_y\biggr|_\mathrm{tip}</math>
&nbsp;
   </td>
   </td>
   <td align="center">
   <td align="center">
Line 1,813: Line 2,284:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~v_y|_\mathrm{body}\cdot \cos\theta + v_z|_\mathrm{body}\cdot \sin\theta</math>
<math>~
C_B +
\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr]
+ \frac{1}{2} \Omega_f^2(x^2 + y^2)
+ \frac{1}{2} \lambda^2(x^2 + y^2) 
- \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) 
</math>
   </td>
   </td>
</tr>
</tr>
Line 1,825: Line 2,302:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 x \cdot \cos\theta - \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 x \cdot \sin\theta</math>
<math>~
-\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_3 c^2 \biggr] +
\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr]
+ \frac{1}{2} \Omega_f^2(x^2 + y^2)
+ \frac{1}{2} \lambda^2(x^2 + y^2
- \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) 
</math>
   </td>
   </td>
</tr>
</tr>
Line 1,837: Line 2,320:
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~x_t \biggl\{ \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta - \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta \biggr\} \, .</math>
<math>~
\pi G \rho \biggl[A_3 c^2  - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr]
+ \frac{ (\Omega_f^2+\lambda^2) }{2} \biggl[ x^2 + y^2\biggr]  
- \Omega_f \lambda \biggl[ \biggl(\frac{b}{a}\biggr) x^2 + \biggl( \frac{a}{b} \biggr)y^2 \biggr] 
</math>
   </td>
   </td>
</tr>
</tr>
</table>
Now, following our [[#Initial_Thoughts|earlier analysis for ''S-Type'' ellipsoids]], let's assume that,
<div align="center">
<math>~x_t = x_\mathrm{max}\cos(\varphi t)</math> &nbsp; &nbsp; &nbsp; and,  &nbsp; &nbsp; &nbsp; <math>~y_t = y_0 - y_\mathrm{max}\sin(\varphi t) \, .</math>
</div>
(Insertion of the extra term, y<sub>0</sub>, acknowledges that the center of the elliptical orbit in the "tipped" plane will be shifted off of the x-axis in the y<sub>t</sub>-direction; the size of this shift should correlate with z<sub>t</sub>, that is, with the vertical location of the tipped plane.)  We have, then,
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~v_y\biggr|_\mathrm{tip} = \frac{dy_t}{dt} = -y_\mathrm{max} \varphi \cos(\varphi t)</math>
<math>~\Rightarrow~~~ \frac{c^2}{a^2 (\pi G\rho)}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
<math>~\sim</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~x_\mathrm{max} \cos(\varphi t) \biggl\{ \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta - \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta \biggr\} \, ,</math>
<math>~
\frac{ (\Omega_f^2+\lambda^2) }{2(\pi G \rho)} \biggl[ \biggl(\frac{x}{a}\biggr)^2 + \biggl( \frac{y}{a}\biggr)^2\biggr]
- \frac{\Omega_f \lambda}{(\pi G \rho)} \biggl[ \biggl(\frac{b}{a}\biggr) \biggl( \frac{x}{a}\biggr)^2 + \biggl( \frac{a}{b} \biggr) \biggl( \frac{y}{a}\biggr)^2 \biggr] 
- \biggl[A_1 \biggl( \frac{x}{a}\biggr)^2 + A_2 \biggl(\frac{y}{a}\biggr)^2 +A_3 \biggl( \frac{z^2 - c^2}{a^2}\biggr\biggr] \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
Drawing from equation (7) of [https://ui.adsabs.harvard.edu/abs/2006ApJ...639..549O/abstract Ou (2006)] and from a [[User:Tohline/ThreeDimensionalConfigurations/HomogeneousEllipsoids#Gravitational_Potential|separate discussion of gravitational potential of homogeneous ellipsoids]], we see that the effective potential is,
<div align="center">
<math>
~\Phi_\mathrm{eff}(\vec{x})\equiv \Phi + \Psi = -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr]
+ \omega\lambda \biggl( \frac{b}{a}x^2 + \frac{a}{b} y^2\biggr) - \frac{\omega^2}{2}\biggl( x^2 + y^2\biggr) -\frac{\lambda^2}{2}\biggl(x^2 + y^2\biggr) \, ,
</math><br />
</div>
where,
<table align="center" border=0 cellpadding="3">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~v_x\biggr|_\mathrm{tip} = \frac{dx_t}{dt} = -x_\mathrm{max}\varphi \sin(\varphi t)</math>
<math>
~I_\mathrm{BT}
</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
<math>
~\equiv
</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>
\biggl[ y_0 - y_\mathrm{max} \sin(\varphi t) \biggr]\biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
~A_1 + A_2\biggl(\frac{b}{a}\biggr)^2+ A_3\biggl(\frac{c}{a}\biggr)^2 \, .
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
+ z_t\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \sin\theta
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \cos\theta  \biggr\} \, .
</math>
</math>
   </td>
   </td>
</tr>
</tr>
</table>


Setting <math>~\pi G \rho = 1</math>, let's use the test case from above &#8212; that is, (b/a, c/a) = (0.9, 0.641) &#8212; and see if we get the same value of the Bernoulli constant on the surface at each of the three principal axes.  First, let's set x = y = 0 and z = c.  In this case <math>~I_\mathrm{BT} = 1.36658564</math> we find,
<table border="0" align="center" cellpadding="8">
<tr>
<tr>
  <td align="right">
<td align="right">
&nbsp;
<math>~\Phi_\mathrm{eff}</math>
  </td>
</td>
  <td align="center">
<td align="center">
<math>~=</math>
<math>~=</math>
  </td>
</td>
  <td align="left">
<td align="left">
<math>~
<math>~\biggl[1.36658564 - 0.36298  \biggr] = 1.00350567 \, .</math>
- y_\mathrm{max} \sin(\varphi t) \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
</td>
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
&nbsp;
  </td>
  <td align="left">
<math>~
+ y_0  \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
+ z_t\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \sin\theta
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \cos\theta  \biggr\} \, .
</math>
  </td>
</tr>
</tr>
</table>
</table>
So, in terms of the value of z<sub>t</sub>, the offset in y<sub>t</sub> must be,
<table border="0" cellpadding="5" align="center">


Next, let's set y = z = 0 and x = 1.  In this case,
<table border="0" align="center" cellpadding="8">
<tr>
<tr>
  <td align="right">
<td align="right">
<math>~ - y_0  \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
<math>~\Phi_\mathrm{eff}</math>
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
</td>
</math>
<td align="center">
  </td>
  <td align="center">
<math>~=</math>
<math>~=</math>
  </td>
</td>
  <td align="left">
<td align="left">
<math>~
<math>~\biggl[1.36658564 - 0.52145027  \biggr] + 0.10151682 -0.64000 - 0.01136605 = 0.29518175 \, .</math>
+ z_t\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \sin\theta
</td>
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \cos\theta  \biggr\} \, ;
</math>
  </td>
</tr>
</tr>
</table>
</table>
in which case,
<table border="0" cellpadding="5" align="center">


=''S-Type Ellipsoid'' Example b41c385=
<div align="center">
<table border="1" align="center" cellpadding="8">
<tr>
<tr>
   <td align="right">
   <th align="center">Figure 1a</th>
<math>~ -y_\mathrm{max} \varphi \cos(\varphi t)</math>
  <th align="center">Figure 1b</th>
</tr>
<tr>
  <td align="left" bgcolor="lightgrey">
[[File:EFEb41c385.view2.cropped.png|400px|EFE Model b41c385]]
   </td>
   </td>
   <td align="center">
   <td align="left" bgcolor="lightgrey">
<math>~=</math>
[[File:EFEb41c385.view1.cropped.png|400px|EFE Model b41c385]]
  </td>
  <td align="left">
<math>~x_\mathrm{max} \cos(\varphi t) \biggl\{ \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta - \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta \biggr\} \, ,</math>
   </td>
   </td>
</tr>
</tr>
</table>
</div>
The EFE model that we chose to use in our first successful construction of a COLLADA-based, 3D and interactive animation had the following properties (model selected from the above table):
<ul>
  <li><math>~b/a = 0.41</math></li>
  <li><math>~c/a = 0.385</math></li>
  <li><math>~\Omega_\mathrm{EFE} = \omega/\sqrt\pi = 0.971082/\sqrt\pi = 0.547874</math></li>
  <li><math>~\lambda_\mathrm{EFE} = 0.141594/\sqrt\pi = 0.079886</math></li>
</ul>
Figure 1 displays a pair of still-frame images of this (purple) ellipsoidal configuration after the ellipsoid has completed precisely five (counter-clockwise) spin cycles.  (The snapshots have been taken at the same point in time, but from two different "camera" viewing angles.)  The cycle of the "wall mounted" clock is based on the fundamental, EFE-adopted frequency of [&pi; G &rho;]<sup>½</sup>.  In the left-hand image (labeled Figure 1a),  the time on the clock appears to be about 9:08.  This means that as the ellipsoid has completed five spin cycles, the clock has completed approximately [9 + 8/60] &#8776; 9.13 cycles.  In other words, the ratio (ellipsoid-to-clock) of these two frequencies is,
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~ \Rightarrow ~~~ \varphi </math>
<math>~\frac{\Omega_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
<math>~\approx</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~-\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl\{ \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta - \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta \biggr\} \, ,</math>
<math>~\frac{5}{9.13} = 0.548 \, .</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
and,
 
This matches the tabulated value of <math>~\Omega_\mathrm{EFE}</math> presented above.  Now, let's examine the motion of an example Lagrangian fluid element, which has been marked in the 3D scene by a red "arrow" riding in the equatorial plane and along the surface of the (purple) ellipsoidal figure.  At time zero, the fluid marker was placed at the end of the longest axis of the ellipsoid that was nearest the "wall clock"; then, as time progressed and the ellipsoidal figure turned counter-clockwise, the fluid marker moved clockwise and completed less than one full "orbit" in the same time that the ellipsoidal figure completed five full spin cycles.  In the right-hand image (labeled Figure 1b), we can see that ''relative'' to the ellipsoidal figure, the fluid marker has moved through approximately three-quarters of its assigned elliptical "orbit"; let's say, 73% of one full cycle.  This means that the ratio of the Lagrangian fluid element's orbital frequency to the frequency of the wall-clock is,
<table border="0" cellpadding="5" align="center">
<table border="0" cellpadding="5" align="center">


<tr>
<tr>
   <td align="right">
   <td align="right">
<math>~-x_\mathrm{max}\varphi \sin(\varphi t)</math>
<math>~\frac{\lambda_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>
   </td>
   </td>
   <td align="center">
   <td align="center">
<math>~=</math>
<math>~\approx</math>
   </td>
   </td>
   <td align="left">
   <td align="left">
<math>~
<math>~\frac{0.73}{9.13} = 0.080 \, .</math>
- y_\mathrm{max} \sin(\varphi t) \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~ \varphi </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]\biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\} \, .
</math>
   </td>
   </td>
</tr>
</tr>
</table>
</table>
In order for both of these expressions to be simultaneously true, we need,


<table border="0" cellpadding="5" align="center">
This matches the tabulated value of <math>~\lambda_\mathrm{EFE}</math> presented above.


<tr>
  <td align="right">
<math>~\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl\{ \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta - \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta \biggr\}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]\biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta \biggr\}
</math>
  </td>
</tr>


<tr>
=See Also=
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta 
-
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
\biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta
</math>
  </td>
</tr>


<tr>
* Discussion of [[User:Tohline/ThreeDimensionalConfigurations/RiemannStype|Ou's Riemann-Like Ellipsoids]]
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \sin\theta 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \cdot \cos\theta
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
\biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \cos\theta
</math>
  </td>
</tr>


<tr>
* [[User:Tohline/ThreeDimensionalConfigurations/MeetsCOLLADAandOculusRiftS|Riemann Meets COLLADA &amp; Oculus Rift S]]
  <td align="right">
** [[User:Tohline/Appendix/Ramblings/VirtualReality#Virtual_Reality_and_3D_Printing|Virtual Reality and 3D Printing]]
<math>~\Rightarrow ~~~
** [[User:Tohline/Appendix/Ramblings/OculusRift_S|Success Importing Animated Scene into Oculus Rift S]]
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2
** [[User:Tohline/Appendix/Ramblings/RiemannMeetsOculus|Carefully (Re)Build Riemann Type S Ellipsoids Inside Oculus Rift Environment]]: Example <b>(b/a, c/a) = (0.41, 0.385)</b>
-
** Other Example S-type Riemann Ellipsoids:
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB90C333|(b/a, c/a) = (0.90, 0.333)]]</b>
a^2 \biggl\} \frac{\zeta_2 \sin\theta }{(a^2 + c^2)}
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB74C692|(b/a, c/a) = (0.74, 0.692)]]</b>
</math>
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB28C256|(b/a, c/a) = (0.28, 0.256)]]</b>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
a^2 \biggr\} \frac{\zeta_3 \cos\theta }{(a^2 + b^2)} \, .
</math>
  </td>
</tr>
</table>


==Chandrasekhar's Detailed Analysis==
* [https://books.google.com/books?id=vo9VAAAAYAAJ&pg=PR6&dq=Gesammelte+Mathematische+Werke+B.+Riemann&source=gbs_selected_pages&cad=3#v=onepage&q=Gesammelte%20Mathematische%20Werke%20B.%20Riemann&f=false Bernhard Riemann (1876)] ''Gesammelte Mathematische Werke und Wissenschaftlicher'', especially Chapter X (p. 168) titled (something along the following line), "A Contribution to Research on Rotating Ellipsoidal Fluids"
* [https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract S. Chandrasekhar (1965)], ApJ, 142, 890 - 961.  ''The Equilibrum and the Stability of the Riemann Ellipsoids. I.'' &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXV in EFE]] and focuses on S-type Riemann ellipsoids.
* [https://ui.adsabs.harvard.edu/abs/1966ApJ...145..842C/abstract S. Chandrasekhar (1966)], ApJ, 145, 842 - 877.  ''The Equilibrum and the Stability of the Riemann Ellipsoids. II.'' &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXVIII in EFE]] and focuses on Riemann ellipsoids of Types I, II and III.


===First Trial Value of &theta;===
==Finite-Amplitude Oscillations==
Now, from above, we determined that the "tip" angle must obey the expression,


<table border="0" cellpadding="5" align="center">
* [https://ui.adsabs.harvard.edu/abs/1967ApJ...149..145R/abstract L. F. Rossner (1967)], ApJ, 149, 145. ''The Finite-Amplitude Oscillations of the Maclaurin Spheroids''  &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXXVIII in EFE]].
 
* [https://ui.adsabs.harvard.edu/abs/1968ApJ...152..523F/abstract M. Fujimoto (1968)], ApJ, 152, 523. ''Gravitational Collapse of Rotating Gaseous Ellipsoids''
<tr>
* [https://ui.adsabs.harvard.edu/abs/1995Ap%26SS.229..215C/abstract T. T. Chia &amp; S. Y. Pung (1995)], Astrophysics and Space Science, 229, issue 2, 215 - 233.  ''Effects of Variations of Parallel Angular Velocity and Vorticity on the Oscillations of Compressible Homogeneous Rotating Ellipsoids''
  <td align="right">
* [https://ui.adsabs.harvard.edu/abs/1997Ap%26SS.254..269C/abstract T. T. Chia &amp; S. Y. Pung (1997)], Astrophysics and Space Science, 254, 269 - 294.  ''Dynamical Behaviour of Compressible Homogeneous Uniformly Rotating Ellipsoids with Nonparallel Angular Velocity and Vorticity''
<math>~\tan\theta </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \biggl[ \frac{b^2}{a^2 + b^2} \biggr]^{-1} \zeta_3^{-1} \, .</math>
  </td>
</tr>
</table>
Hence, we require,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 \cdot \biggl[ \frac{b^2}{a^2 + b^2} \biggr]^{-1} \zeta_3^{-1}
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
a^2 \biggl\} \frac{\zeta_2 }{(a^2 + c^2)}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
a^2 \biggr\} \frac{\zeta_3 }{(a^2 + b^2)}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~ \Rightarrow ~~~ 
\biggl\{
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
a^2
-  \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2
\biggl\} \frac{c^2 \zeta_2^2 }{(a^2 + c^2)^2}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]
a^2 \biggr\} \frac{b^2\zeta_3^2 }{(a^2 + b^2)^2}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~ \Rightarrow ~~~ 
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
\frac{a^2 c^2 \zeta_2^2 }{(a^2 + c^2)^2}
-
\frac{c^4 \zeta_2^2 }{(a^2 + c^2)^2}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\frac{b^4 \zeta_3^2 }{(a^2 + b^2)^2}
- \biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
\frac{a^2 b^2\zeta_3^2 }{(a^2 + b^2)^2} \, .
</math>
  </td>
</tr>
</table>
That is,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~ 
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{b^4 \zeta_3^2 }{(a^2 + b^2)^2}
+
\frac{c^4 \zeta_2^2 }{(a^2 + c^2)^2} \biggr]
\biggl[ \frac{a^2 c^2 \zeta_2^2 }{(a^2 + c^2)^2}
+
\frac{a^2 b^2\zeta_3^2 }{(a^2 + b^2)^2} \biggr]^{-1}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ b^4 \zeta_3^2 (a^2 + c^2)^2
+
c^4 \zeta_2^2 (a^2 + b^2)^2 \biggr]
\biggl[ a^2 c^2 \zeta_2^2 (a^2 + b^2)^2
+
a^2 b^2\zeta_3^2 (a^2 + c^2)^2 \biggr]^{-1} \, .
</math>
  </td>
</tr>
</table>
 
So for the example parameters provided above, we have,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~ 
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ 14.04
+
1.669 \biggr]
\biggl[ 7.546 
+
8.985 \biggr]^{-1} = 0.9502
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~  \Rightarrow~~~
\frac{y_\mathrm{max}}{x_\mathrm{max}} 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
0.9748
</math>
  </td>
</tr>
</table>
 
 
===Second Trial Value of &theta;===
 
Instead, what if we obtain the tip angle straight from the tabulated expression,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\tan\theta</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\frac{\zeta_3}{\zeta_2} \, .</math>
  </td>
</tr>
</table>
 
Then we have,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 \biggl\}
\frac{1 }{(a^2 + c^2)}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 \biggr\}
\frac{1 }{(a^2 + b^2)}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2  (a^2 + b^2)
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2  (a^2 + b^2) 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 (a^2 + c^2)
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 (a^2 + c^2)
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow~~~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ c^2  (a^2 + b^2)- b^2 (a^2 + c^2) \biggr]
\biggl[ a^2  (a^2 + b^2)  - a^2 (a^2 + c^2) \biggr]^{-1}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
[ c^2 - b^2 ]
[ b^2  - c^2 ]^{-1} = -1 \, .
</math>
  </td>
</tr>
</table>
 
And this is not physically acceptable.  What if, instead, we set,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\tan\theta</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \frac{\zeta_3}{\zeta_2} ~~~\Rightarrow ~~~ \theta = -40.74^\circ \, .</math>
  </td>
</tr>
</table>
 
Then we have,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~
- \biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 \biggl\}
\frac{1 }{(a^2 + c^2)}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 \biggr\}
\frac{1 }{(a^2 + b^2)}
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
- \biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] c^2  (a^2 + b^2)
+
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2  (a^2 + b^2) 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr]  b^2 (a^2 + c^2)
-
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] a^2 (a^2 + c^2)
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] [ a^2  (a^2 + b^2)  + a^2 (a^2 + c^2) ]
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] [ b^2 (a^2 + c^2) +  c^2  (a^2 + b^2) ]
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
[ b^2 (a^2 + c^2) +  c^2  (a^2 + b^2) ] [ a^2  (a^2 + b^2)  + a^2 (a^2 + c^2) ]^{-1} \, .
</math>
  </td>
</tr>
</table>
 
In our particular example, this means,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr]^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
[ 2.4749 ] [ 3.7837 ]^{-1} = 0.6541
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
\biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \bigg]
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
0.8088 \, .
</math>
  </td>
</tr>
</table>
 
==Try Again==
 
===Methodical Derivation of Orbital Parameters===
Let the unprimed coordinates (x, y, z) represent the body frame of the ellipsoid, and the primed coordinates (x', y', z') represent a coordinate system in which the z'-axis is "tipped" &#8212; about the x' = x axis &#8212; away from the z-axis by an angle, &theta;.  We assume that the motion of each Lagrangian fluid element will be restricted to an x'-y' equatorial plane &#8212; that is, we assume that <math>~\dot{z}' \equiv dz'/dt = 0</math> &#8212; but in general its velocity vector in the unprimed "body" frame will have the three nonzero components as specified in EFE and above.  Here are some relevant transformations between these two coordinate systems.
<table border="1" align="center" cellpadding="10">
<tr>
<td align="center">
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~x'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~x \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~y'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y \cos\theta + (z-z_0)\sin\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~z'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~(z-z_0)\cos\theta - y\sin\theta \, .</math>
  </td>
</tr>
</table>
 
</td>
<td align="center">
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~x</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~x' \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~y</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y' \cos\theta - z'\sin\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~z-z_0</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~z'\cos\theta + y'\sin\theta \, .</math>
  </td>
</tr>
</table>
 
</td>
</tr>
 
<tr>
<td align="center">
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\dot{x}'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\dot{x} \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\dot{y}'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\dot{y} \cos\theta + \dot{z}\sin\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\cancelto{0}{\dot{z}'}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\dot{z} \cos\theta - \dot{y}\sin\theta \, .</math>
  </td>
</tr>
</table>
 
</td>
<td align="center">
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\dot{x}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\dot{x}' \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\dot{y}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\dot{y}' \cos\theta - \cancelto{0}{\dot{z}'}\sin\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\dot{z}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\cancelto{0}{\dot{z}'}\cos\theta + \dot{y}'\sin\theta \, .</math>
  </td>
</tr>
</table>
 
</td>
</tr>
 
</table>
 
 
<b><font color="red">NOTE:</font></b>  The center of each elliptical orbit is (x', y', z') = (0, y<sub>0</sub>, 0).  In "body" coordinates, then, (x, y, z) = (0, y<sub>0</sub> cos&theta;, z<sub>0</sub> + y<sub>0</sub> sin&theta;).
 
Focusing on the bottom-right quadrant of this equation-table, we note first that <math>~(\dot{x}, \dot{y}, \dot{z}) = (u_1, u_2, u_3)</math>, as [[#EFEvelocities|provided above from EFE]].  Copying from the upper-right quadrant of this equation-table, let's rewrite these three velocity components in terms of the "tipped" plane coordinates, namely,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\dot{x} = u_1</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \biggl[ y'\cos\theta - z'\sin\theta\biggr]
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl[ z_0 + z'\cos\theta + y'\sin\theta \biggr] \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\dot{y} = u_2</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~+\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 x' \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\dot{z} = u_3</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 x' \, .</math>
  </td>
</tr>
</table>
 
 
Now, if we assume that each Lagrangian particle executes a closed elliptical orbit ''in the plane'' of the tipped coordinate system (''i.e.,'' <math>~z' = \dot{z}' = 0</math> ), but whose orbit-center may be shifted by an amount, <math>~y_0</math>, away from the z'-axis, we expect &hellip;
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~x'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~x_\mathrm{max}\cos(\varphi t)</math>
  </td>
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
  <td align="right">
<math>~y' - y_0</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y_\mathrm{max}\sin(\varphi t) \, ,</math>
  </td>
</tr>
</table>
which implies,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\dot{x}'</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- x_\mathrm{max}~ \varphi \cdot \sin(\varphi t)</math>
  </td>
<td align="center">&nbsp; &nbsp; &nbsp; and, &nbsp; &nbsp; &nbsp;
  <td align="right">
<math>~\dot{y}' </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y_\mathrm{max}~\varphi \cdot \cos(\varphi t) \, .</math>
  </td>
</tr>
</table>
 
The first of these equation pairs can be plugged directly into the expressions for u<sub>1</sub>, u<sub>2</sub>, and u<sub>3</sub> &#8212; further fleshing out the LHS of the equations in the bottom-right quadrant of the above equation-table &#8212; while the second pair can be used to re-express the RHS of the equations in the bottom-right quadrant of this equation table.  We obtain,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \biggl\{  \biggl[ y_0 + y_\mathrm{max} \sin(\varphi t) \biggr] \cos\theta - \cancelto{0}{z'}\sin\theta \biggr\}
+ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl\{ z_0 + \cancelto{0}{z'} \cos\theta + \biggl[ y_0 + y_\mathrm{max} \sin(\varphi t) \biggr]\sin\theta \biggr\} </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~-x_\mathrm{xmax} ~\varphi \cdot \sin(\varphi t) \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~+\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 x_\mathrm{max}\cos(\varphi t) </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y_\mathrm{max}~\varphi \cdot \cos(\varphi t) \cdot \cos\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~- \biggl[ \frac{c^2}{a^2 + c^2} \biggr] \zeta_2 x_\mathrm{max}\cos(\varphi t) </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~y_\mathrm{max}~\varphi \cdot \cos(\varphi t) \cdot \sin\theta \, .</math>
  </td>
</tr>
</table>
 
Combining the second and third of these conditions, we find first that,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\tan\theta </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \frac{\zeta_2 }{ \zeta_3 } \biggl[ \frac{a^2 + b^2}{a^2 + c^2} \biggr]\frac{c^2}{b^2} \, ,</math>
  </td>
</tr>
</table>
 
which gives the "tipping" angle in terms of known parameter values; and second that &hellip; 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\biggl[ \frac{x_\mathrm{max}}{y_\mathrm{max}} \biggr] \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\varphi \cdot \cos\theta \, ,</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~
\varphi \biggl[ \frac{y_\mathrm{max}}{x_\mathrm{max}} \biggr] 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \frac{\zeta_3}{\cos\theta}
\, ,</math>
  </td>
</tr>
</table>
which gives the product of the two unknown quantities, <math>~\varphi</math> and the ratio <math>~y_\mathrm{max}/x_\mathrm{max}</math>, in terms of known parameter values.  And from the first condition, we furthermore find that,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~-x_\mathrm{max} ~\varphi \cdot \sin(\varphi t) </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \biggl[ y_0 \cos\theta \biggr] 
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 \biggl[ y_\mathrm{max} \sin(\varphi t) \biggr] \cos\theta
+
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl[ z_0 + y_0 \sin\theta \biggr]
+
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl[ y_\mathrm{max} \sin(\varphi t) \biggr]\sin\theta 
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~
\Rightarrow ~~~ x_\mathrm{max} ~\varphi \cdot \sin(\varphi t)
+ \biggl\{ \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta 
- \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \cos\theta \biggr\} \biggl[ y_\mathrm{max} \sin(\varphi t) \biggr]
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>
\biggl\{
\biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \biggl[ y_0 \cos\theta \biggr] 
-
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 z_0
-
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl[ y_0 \sin\theta \biggr]
\biggr\} \, .
</math>
  </td>
</tr>
</table>
The LHS and the RHS must separately sum to zero, which means &hellip;
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~
\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \cos\theta   
-
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta  \biggr\}y_0
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 z_0 \, ,
</math>
  </td>
</tr>
</table>
 
which gives the ratio, <math>~y_0/z_0</math> in terms of known parameter values; and,
 
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~
\biggl[ \frac{x_\mathrm{max}}{ y_\mathrm{max} } \biggr] ~\varphi 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \cos\theta 
- \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta  \, ,
</math>
  </td>
</tr>
</table>
which in combination with the just-derived similar product relation can give expressions for both terms, namely,
 
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~
\biggl[ \frac{x_\mathrm{max}}{ y_\mathrm{max} } \biggr]^2 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \cos\theta 
- \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta  \biggr\}\biggl[ \frac{a^2 + b^2}{b^2} \biggr] \frac{\cos\theta}{\zeta_3}
\, ,
</math>
  </td>
</tr>
</table>
and,
 
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~
\varphi^2
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~
\biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3 
- \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \tan\theta  \biggr\}\biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3
\, .
</math>
  </td>
</tr>
</table>
 
===Example Implementation===
 
<span id="Tipped">Drawing from</span> the set of [[#Case_I|''Case I'' parameters listed above]],  we will set a = 1, b = 1.25, c = 0.4703, &zeta;<sub>2</sub> = -2.2794, and &zeta;<sub>3</sub> = -1.9637.  This means that,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\tan\theta </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~- \frac{\zeta_2 }{ \zeta_3 } \biggl[ \frac{a^2 + b^2}{a^2 + c^2} \biggr]\frac{c^2}{b^2} = - 0.3448 ~~~\Rightarrow ~~~ \theta = -19.02^\circ
\, .</math>
  </td>
</tr>
</table>
 
We deduce as well that,
<table border="0" cellpadding="5" align="center">
<tr>
  <td align="right">
<math>~
\frac{y_0}{z_0}
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>
\biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \biggl\{ \biggl[ \frac{a^2}{a^2 + b^2} \biggr] \zeta_3  \cos\theta  - \biggl[ \frac{a^2}{a^2 + c^2} \biggr] \zeta_2 \sin\theta  \biggr\}^{-1}
= -1.8666 \cdot \{-0.7245 - 0.6084 \}^{-1} = 1.4004
\, ;
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~
\frac{x_\mathrm{max}}{ y_\mathrm{max} } 
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\biggl\{
\biggl[ \biggl( \frac{a^2}{a^2 + b^2} \biggr) \zeta_3  \cos\theta 
- \biggl( \frac{a^2}{a^2 + c^2} \biggr) \zeta_2 \sin\theta  \biggr] \biggl[ \frac{a^2 + b^2}{b^2} \biggr] \frac{\cos\theta}{\zeta_3} \biggr\}^{1 / 2}
= \{ [-1.3329] \cdot (-0.7895) \}^{1 / 2} = \sqrt{1.0524} = 1.0259
\, ;
</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~
\varphi
</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\biggl\{
\biggl[ \biggl( \frac{a^2}{a^2 + b^2} \biggr) \zeta_3 
- \biggl( \frac{a^2}{a^2 + c^2} \biggr) \zeta_2 \tan\theta  \biggr] \biggl[ \frac{b^2}{a^2 + b^2} \biggr] \zeta_3 \biggr\}^{1 / 2} = 1.2993
\, .
</math>
  </td>
</tr>
</table>
 
<table border="1" cellpadding="10" align="center" width="80%">
<tr><td align="left">
It is important to keep in mind that each Lagrangian fluid element will complete one full orbit in its "tipped" plane when  <math>~\varphi t = 2\pi</math>, where <math>~t</math> is in units of <math>~[\pi G \rho]^{-1 / 2}</math> and <math>~\varphi</math>  is in units of <math>~[\pi G \rho]^{+1 / 2}</math>.  Note, as well, that in our COLLADA animations, we have adopted the convention that <math>~t = 1</math> when <math>~\mathrm{TIME} = 4</math>.  Hence, one complete orbit will be completed when,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~\frac{1}{4} \cdot \mathrm{TIME}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\frac{2\pi}{\varphi} \, .</math>
  </td>
</tr>
</table>
That is to say, in the specific example being used here, on complete orbit is concluded when TIME = 19.343.
</td>
</tr></table>
 
Referring back to our [[#TippedPlane|earlier geometric prescription of a "tipped plane"]] we insert this new slope having m = tan&theta; = -0.3448, and choose a particular plane by setting a value of z<sub>0</sub>.  Then we can map out a locus of points that show the intersection of the chosen plane with the surface of the ellipsoid by specifying various values of z, then calculating the corresponding values of y and x via the respective equations:
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~y </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\frac{1}{\tan\theta} \biggl[ z - z_0 \biggr] \, ;</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\frac{x}{a} </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\biggl[ 1 - \biggl(\frac{z_0}{b \tan\theta}\biggr)^2 \biggl( \frac{z}{z_0} - 1 \biggr)^2 - \biggl( \frac{z}{c} \biggr)^2 \biggr]^{1 / 2} \, .</math>
  </td>
</tr>
</table>
 
For each specified value of z<sub>0</sub>, the relevant range of z values is given by the pair of values for which x/a = 0.  For example, if we set z_0 = b tan&theta; = -0.4310, this pair is given by the roots of the quadratic expression,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~1 </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\biggl( \frac{z}{z_0} - 1 \biggr)^2 + \biggl( \frac{z}{c} \biggr)^2  </math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~ 0 </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~z^2\biggl[ \frac{1}{z_0^2} + \frac{1}{c^2} \biggr] -\frac{2z}{z_0} </math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~z \biggl\{ z - \biggl[ \frac{2 z_0 c^2}{(c^2 + z_0^2)} \biggr] \biggr\} \biggl[ \frac{(c^2 + z_0^2)}{c^2 z_0^2} \biggr] \, .</math>
  </td>
</tr>
</table>
 
The roots are, then, <math>~z_\mathrm{max} = 0</math>, and
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~z_\mathrm{min}</math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~\frac{2 z_0 c^2}{(c^2 + z_0^2)} = -0.468514 \, .</math>
  </td>
</tr>
</table>
 
<span id="ExampleTrajectories">The middle three columns</span> (table cells having bgcolor="lightblue") in the following table list values of |x| and y that correspond to various values of z that lie between this pair of limiting values.
<table border="1" cellpadding="8" align="center">
<tr>
  <th align="center" colspan="11"><math>~m = \tan\theta = -0.3448 ~~~ \Rightarrow ~~~ \theta = -19.02^\circ</math></th>
</tr>
<tr>
  <td align="center" colspan="3">z_0 = -0.2500</td>
  <th align="center" rowspan="18">&nbsp;</th>
  <td align="center" colspan="3">z_0 = b tan&theta; = -0.4310</td>
  <th align="center" rowspan="18">&nbsp;</th>
  <td align="center" colspan="3">z_0 = -0.6000</td>
</tr>
<tr>
  <th align="center">z</th>
  <th align="center">y</th>
  <th align="center">|x|</th>
  <th align="center">z</th>
  <th align="center">y</th>
  <th align="center">|x|</th>
  <th align="center">z</th>
  <th align="center">y</th>
  <th align="center">|x|</th>
</tr>
<tr>
  <td align="center">0.1564</td><td align="center">-1.1788</td><td align="center">0.0000</td>
  <td align="center" bgcolor="lightblue">0</td>  <td align="center" bgcolor="lightblue">-1.2500</td>  <td align="center" bgcolor="lightblue">0</td>
  <td align="center">-0.2182</td><td align="center">-1.1073</td><td align="center">0.0000</td>
</tr>
<tr>
  <td align="center">0.1147</td><td align="center">-1.0577</td><td align="center">0.4739</td>
  <td align="center" bgcolor="lightblue">-0.02</td>  <td align="center" bgcolor="lightblue">- 1.1920</td>  <td align="center" bgcolor="lightblue">0.2981</td>
  <td align="center">-0.2336</td><td align="center">-1.0626</td><td align="center">0.1749</td>
</tr>
<tr>
  <td align="center">0.0729</td><td align="center">-0.9366</td><td align="center">0.6439</td>
  <td align="center" bgcolor="lightblue">-0.05</td>  <td align="center" bgcolor="lightblue">-1.1050</td>  <td align="center" bgcolor="lightblue">0.4553</td>
  <td align="center">-0.2490</td><td align="center">-1.0179</td><td align="center">0.2377</td>
</tr>
<tr>
  <td align="center">0.0312</td><td align="center">-0.8155</td><td align="center">0.7550</td>
  <td align="center" bgcolor="lightblue">-0.08</td>  <td align="center" bgcolor="lightblue">-1.0180</td>  <td align="center" bgcolor="lightblue">0.5548</td>
  <td align="center">-0.2645</td><td align="center">-0.9732</td><td align="center">0.2787</td>
</tr>
<tr>
  <td align="center">-0.0106</td><td align="center">-0.6943</td><td align="center">0.8312</td>
  <td align="center" bgcolor="lightblue">-0.1</td>  <td align="center" bgcolor="lightblue">-0.9600</td>  <td align="center" bgcolor="lightblue">0.6042</td>
  <td align="center">-0.2799</td><td align="center">-0.9285</td><td align="center">0.3068</td>
</tr>
<tr>
  <td align="center">-0.0524</td><td align="center">-0.5732</td><td align="center">0.8817</td>
  <td align="center" bgcolor="lightblue">-0.125</td>  <td align="center" bgcolor="lightblue">-0.8875</td>  <td align="center" bgcolor="lightblue">0.6521</td>
  <td align="center">-0.2953</td><td align="center">-0.8838</td><td align="center">0.3255</td>
</tr>
<tr>
  <td align="center">-0.0941</td><td align="center">-0.4521</td><td align="center">0.9106</td>
  <td align="center" bgcolor="lightblue">-0.15</td>  <td align="center" bgcolor="lightblue">-0.8150</td>  <td align="center" bgcolor="lightblue">0.6879</td>
  <td align="center">-0.3107</td><td align="center">-0.8390</td><td align="center">0.3361</td>
</tr>
<tr>
  <td align="center">-0.1359</td><td align="center">-0.3310</td><td align="center">0.9200</td>
  <td align="center" bgcolor="lightblue">-0.175</td>  <td align="center" bgcolor="lightblue">-0.7424</td>  <td align="center" bgcolor="lightblue">0.7133</td>
  <td align="center">-0.3261</td><td align="center">-0.7943</td><td align="center">0.3396</td>
</tr>
<tr>
  <td align="center">-0.1776</td><td align="center">-0.2099</td><td align="center">0.9106</td>
  <td align="center" bgcolor="lightblue">-0.2</td>  <td align="center" bgcolor="lightblue">- 0.6699</td>  <td align="center" bgcolor="lightblue">0.7293</td>
  <td align="center">-0.3415</td><td align="center">-0.7496</td><td align="center">0.3361</td>
</tr>
<tr>
  <td align="center">-0.2194</td><td align="center">-0.0887</td><td align="center">0.8817</td>
  <td align="center" bgcolor="lightblue">-0.25</td>  <td align="center" bgcolor="lightblue">- 0.5249</td>  <td align="center" bgcolor="lightblue">0.7356</td>
  <td align="center">-0.3570</td><td align="center">-0.7049</td><td align="center">0.3255</td>
</tr>
<tr>
  <td align="center">-0.2612</td><td align="center">0.0324</td><td align="center">0.8312</td>
  <td align="center" bgcolor="lightblue">-0.30</td>  <td align="center" bgcolor="lightblue">- 0.3799</td>  <td align="center" bgcolor="lightblue">0.7076</td>
  <td align="center">-0.3724</td><td align="center">-0.6602</td><td align="center">0.3068</td>
</tr>
<tr>
  <td align="center">-0.3029</td><td align="center">0.1535</td><td align="center">0.7550</td>
  <td align="center" bgcolor="lightblue">-0.35</td>  <td align="center" bgcolor="lightblue">- 0.2349</td>  <td align="center" bgcolor="lightblue">0.6410</td>
  <td align="center">-0.3878</td><td align="center">-0.6155</td><td align="center">0.2787</td>
</tr>
<tr>
  <td align="center">-0.3447</td><td align="center">0.2746</td><td align="center">0.6439</td>
  <td align="center" bgcolor="lightblue">-0.4</td>  <td align="center" bgcolor="lightblue">- 0.0899</td>  <td align="center" bgcolor="lightblue">0.5210</td>
  <td align="center">-0.4032</td><td align="center">-0.5708</td><td align="center">0.2377</td>
</tr>
<tr>
  <td align="center">-0.3865</td><td align="center">0.3957</td><td align="center">0.4739</td>
  <td align="center" bgcolor="lightblue">-0.43</td>  <td align="center" bgcolor="lightblue">- 0.0029</td>  <td align="center" bgcolor="lightblue">0.4050</td>
  <td align="center">-0.4186</td><td align="center">-0.5261</td><td align="center">0.1749</td>
</tr>
<tr>
  <td align="center">-0.4282</td><td align="center">0.5169</td><td align="center">0.0</td>
  <td align="center" bgcolor="lightblue">-0.46</td>  <td align="center" bgcolor="lightblue">+0.0841</td>  <td align="center" bgcolor="lightblue">0.1950</td>
  <td align="center">-0.4340</td><td align="center">-0.4814</td><td align="center">0.0000</td>
</tr>
<tr>
  <td align="center" colspan="3">&nbsp;</td>
  <td align="center" bgcolor="lightblue">-0.4685</td>  <td align="center" bgcolor="lightblue">+0.1088</td>  <td align="center" bgcolor="lightblue">0.0081</td>
  <td align="center" colspan="3">&nbsp;</td>
</tr>
</table>
 
 
More generally, letting <math>~q \equiv z_0/(b\tan\theta)</math>, the pair of limiting values of z are given by the roots of the quadratic expression,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~1 </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~q^2 \biggl( \frac{z}{z_0} - 1 \biggr)^2 + \biggl( \frac{z}{c} \biggr)^2  </math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~0 </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~ z^2 \biggl[ \frac{ q^2c^2 + z_0^2)}{z_0^2 q^2 c^2} \biggr]  - \frac{2z}{z_0}    + \biggl[ 1  - \frac{1}{q^2} \biggr] \, .</math>
  </td>
</tr>
</table>
 
That is,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~z </math>
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~ \biggl[ \frac{z_0^2 q^2 c^2}{ 2(q^2 c^2 + z_0^2)} \biggr]\biggl\{ \frac{2}{z_0}  \pm  \biggl[\frac{4}{z_0^2} -  \frac{ 4 (1  - q^{-2})(q^2 c^2 + z_0^2)}{z_0^2 q^2 c^2} \biggr]^{1 / 2} \biggr\} </math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~=</math>
  </td>
  <td align="left">
<math>~ \biggl[ \frac{z_0 q^2 c^2}{ (q^2 c^2 + z_0^2)} \biggr]\biggl\{ 1  \pm  \biggl[1 -  \frac{ (1  - q^{-2})(q^2 c^2 + z_0^2)}{ q^2 c^2} \biggr]^{1 / 2} \biggr\} \, .</math>
  </td>
</tr>
</table>
And we see that the constraint set on z<sub>0</sub> is given by the condition,
 
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~1</math>
  </td>
  <td align="center">
<math>~\ge</math>
  </td>
  <td align="left">
<math>~\frac{ (1  - q^{-2})(q^2c^2 + z_0^2)}{q^2c^2} </math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~ q^2 c^2</math>
  </td>
  <td align="center">
<math>~\ge</math>
  </td>
  <td align="left">
<math>~(1  - q^{-2})(q^2c^2 + z_0^2) </math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~\ge</math>
  </td>
  <td align="left">
<math>~(q^2 - 1)(c^2 + b^2\tan^2\theta) </math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~ 0</math>
  </td>
  <td align="center">
<math>~\ge</math>
  </td>
  <td align="left">
<math>~ (q^2 - 1)b^2\tan^2\theta - c^2</math>
  </td>
</tr>
 
<tr>
  <td align="right">
&nbsp;
  </td>
  <td align="center">
<math>~\ge</math>
  </td>
  <td align="left">
<math>~ z_0^2 - c^2 - b^2\tan^2\theta</math>
  </td>
</tr>
 
<tr>
  <td align="right">
<math>~\Rightarrow ~~~ z_0^2</math>
  </td>
  <td align="center">
<math>~\le</math>
  </td>
  <td align="left">
<math>~ c^2 + b^2\tan^2\theta \, .</math>
  </td>
</tr>
</table>
 
Therefore, for this example Type I ellipsoidal configuration, z<sub>0</sub> must lie within the range,
<table border="0" cellpadding="5" align="center">
 
<tr>
  <td align="right">
<math>~-0.650165</math>
  </td>
  <td align="center">
<math>~\le z_0 \le</math>
  </td>
  <td align="left">
<math>~+0.650165 \, .</math>
  </td>
</tr>
</table>
In the [[#ExampleTrajectories|above table]], we have detailed the loci of points along the surface trajectories that correspond to the values, z<sub>0</sub> = - 0.2500 (the leftmost three columns of the table) and z<sub>0</sub> = -0.6000 (the rightmost three columns of the table).  The limiting values of z for these to choices of z<sub>0</sub> are, respectively, [z<sub>min</sub> = -0.4283, z<sub>max</sub> = +0.1564] and  [z<sub>min</sub> = -0.4340, z<sub>max</sub> = -0.2182].
 
<span id="Figure3">Using COLLADA,</span> we have constructed an animated and interactive 3D scene that displays in purple the surface of our example Type I ellipsoid; panels a and b of Figure 3 show what this ellipsoid looks like when viewed from two different perspectives.  (As a reminder &#8212; see the [[#explanation| explanation accompanying Figure 2, above]] &#8212; the ellipsoid is tilted about the x-coordinate axis at an angle of 61.25&deg; to the equilibrium spin axis, which is shown in green.)  Yellow markers also have been placed in this 3D scene at each of the coordinate locations specified in the  [[#ExampleTrajectories|above table]].  From the perspective presented in Figure 3b, we can immediately identify three separate, nearly circular trajectories; the largest one corresponds to our choice of z<sub>0</sub> = -0.25, the smallest corresponds to our choice of z<sub>0</sub> = -0.60, and the one of intermediate size correspond to our choice of z<sub>0</sub> = -0.4310.  When viewed from the perspective presented in Figure 3a, we see that these three trajectories define three separate planes; each plane is tipped at an angle of &theta; = -19.02&deg; to the ''untilted'' equatorial, x-y plane of the purple ellipsoid.
 
<div align="center">
<table border="1" align="center" cellpadding="8">
<tr>
  <th align="center">Figure 3a</th>
  <th align="center">Figure 3b</th>
</tr>
<tr>
  <td align="left" bgcolor="lightgrey">
[[File:B125c470B.cropped.png|400px|EFE Model b41c385]]
  </td>
  <td align="left" bgcolor="lightgrey">
[[File:B125c470A.cropped.png|400px|EFE Model b41c385]]
  </td>
</tr>
<tr>
  <th align="center" colspan="2">Figure 3c</th>
</tr>
<tr>
  <td align="center" bgcolor="white" colspan="2">
[[File:ProjectedOrbitsFlipped2.png|600px|EFE Model b41c385]]
  </td>
</tr>
</table>
</div>
 
As we have created each orbit in the xml-based COLLADA file, we have first manually typed in the (TIME, x, y, z) coordinates of each orbit that has a ''negative'' value of z<sub>0</sub>.  Specifically, using the Figure 3c projection as a guide/reference, we typed in coordinates for the following orbits:
<ul>
  <li><b>FLUID ELEMENT 1:</b>&nbsp; <math>~z_0 = -0.6000</math></li>
</ul>
 
<table border="1" cellpadding="8" align="center">
<tr>
  <td align="center">nstep</td>
  <td align="center">TIME</td>
  <td align="center">x</td>
  <td align="center">y</td>
  <td align="center">z</td>
</tr>
<tr>
  <td align="center">1</td>
  <td align="center">0.000</td>
  <td align="center">0.000</td>
  <td align="center">-1.107</td>
  <td align="center">-0.218</td>
</tr>
<tr>
  <td align="center">26</td>
  <td align="center">4.836</td>
  <td align="center">-0.340</td>
  <td align="center">-0.794</td>
  <td align="center">-0.326</td>
</tr>
<tr>
  <td align="center">51</td>
  <td align="center">9.672</td>
  <td align="center">0.000</td>
  <td align="center">-0.481</td>
  <td align="center">-0.434</td>
</tr>
<tr>
  <td align="center">76</td>
  <td align="center">14.507</td>
  <td align="center">+0.340</td>
  <td align="center">-0.794</td>
  <td align="center">-0.326</td>
</tr>
<tr>
  <td align="center">101</td>
  <td align="center">19.343</td>
  <td align="center">0.000</td>
  <td align="center">-1.107</td>
  <td align="center">-0.218</td>
</tr>
</table>
 
<ul>
  <li><b>FLUID ELEMENT 2:</b>&nbsp; <math>~z_0 = -0.4300</math></li>
</ul>
 
=See Also=
 
* Discussion of [[User:Tohline/ThreeDimensionalConfigurations/RiemannStype|Ou's Riemann-Like Ellipsoids]]
 
* [[User:Tohline/ThreeDimensionalConfigurations/MeetsCOLLADAandOculusRiftS|Riemann Meets COLLADA &amp; Oculus Rift S]]
** [[User:Tohline/Appendix/Ramblings/VirtualReality#Virtual_Reality_and_3D_Printing|Virtual Reality and 3D Printing]]
** [[User:Tohline/Appendix/Ramblings/OculusRift_S|Success Importing Animated Scene into Oculus Rift S]]
** [[User:Tohline/Appendix/Ramblings/RiemannMeetsOculus|Carefully (Re)Build Riemann Type S Ellipsoids Inside Oculus Rift Environment]]: Example <b>(b/a, c/a) = (0.41, 0.385)</b>
** Other Example S-type Riemann Ellipsoids:
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB90C333|(b/a, c/a) = (0.90, 0.333)]]</b>
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB74C692|(b/a, c/a) = (0.74, 0.692)]]</b>
*** <b>[[User:Tohline/Appendix/Ramblings/RiemannB28C256|(b/a, c/a) = (0.28, 0.256)]]</b>
 
==Chandrasekhar's Detailed Analysis==
* [https://books.google.com/books?id=vo9VAAAAYAAJ&pg=PR6&dq=Gesammelte+Mathematische+Werke+B.+Riemann&source=gbs_selected_pages&cad=3#v=onepage&q=Gesammelte%20Mathematische%20Werke%20B.%20Riemann&f=false Bernhard Riemann (1876)] ''Gesammelte Mathematische Werke und Wissenschaftlicher'', especially Chapter X (p. 168) titled (something along the following line), "A Contribution to Research on Rotating Ellipsoidal Fluids"
* [https://ui.adsabs.harvard.edu/abs/1965ApJ...142..890C/abstract S. Chandrasekhar (1965)], ApJ, 142, 890 - 961.  ''The Equilibrum and the Stability of the Riemann Ellipsoids. I.'' &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXV in EFE]] and focuses on S-type Riemann ellipsoids.
* [https://ui.adsabs.harvard.edu/abs/1966ApJ...145..842C/abstract S. Chandrasekhar (1966)], ApJ, 145, 842 - 877.  ''The Equilibrum and the Stability of the Riemann Ellipsoids. II.'' &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXVIII in EFE]] and focuses on Riemann ellipsoids of Types I, II and III.
 
==Finite-Amplitude Oscillations==
 
* [https://ui.adsabs.harvard.edu/abs/1967ApJ...149..145R/abstract L. F. Rossner (1967)], ApJ, 149, 145. ''The Finite-Amplitude Oscillations of the Maclaurin Spheroids''  &#8212; This work is referenced as [[User:Tohline/Appendix/References#Appendix_of_EFE|Paper XXXVIII in EFE]].
* [https://ui.adsabs.harvard.edu/abs/1968ApJ...152..523F/abstract M. Fujimoto (1968)], ApJ, 152, 523. ''Gravitational Collapse of Rotating Gaseous Ellipsoids''
* [https://ui.adsabs.harvard.edu/abs/1995Ap%26SS.229..215C/abstract T. T. Chia &amp; S. Y. Pung (1995)], Astrophysics and Space Science, 229, issue 2, 215 - 233.  ''Effects of Variations of Parallel Angular Velocity and Vorticity on the Oscillations of Compressible Homogeneous Rotating Ellipsoids''
* [https://ui.adsabs.harvard.edu/abs/1997Ap%26SS.254..269C/abstract T. T. Chia &amp; S. Y. Pung (1997)], Astrophysics and Space Science, 254, 269 - 294.  ''Dynamical Behaviour of Compressible Homogeneous Uniformly Rotating Ellipsoids with Nonparallel Angular Velocity and Vorticity''


==In the Context of Galaxy Disks==
==In the Context of Galaxy Disks==
Line 3,534: Line 2,501:
* [[User:Tohline/Apps/MaclaurinSpheroids#Maclaurin_Spheroids_.28axisymmetric_structure.29|Properties of Maclaurin Spheroids]]
* [[User:Tohline/Apps/MaclaurinSpheroids#Maclaurin_Spheroids_.28axisymmetric_structure.29|Properties of Maclaurin Spheroids]]
* [[User:Tohline/Apps/MaclaurinSpheroids/GoogleBooks#Excerpts_from_A_Treatise_of_Fluxions|Excerpts from Maclaurin's (1742) ''A Treatise of Fluxions'']]
* [[User:Tohline/Apps/MaclaurinSpheroids/GoogleBooks#Excerpts_from_A_Treatise_of_Fluxions|Excerpts from Maclaurin's (1742) ''A Treatise of Fluxions'']]
=Footnotes=
<ol type="1">
<li>In [[User:Tohline/Appendix/References#EFE|EFE]] this equation is written in terms of a variable <math>~I</math> instead of <math>~I_\mathrm{BT}</math> as defined here.  The two variables are related to one another straightforwardly through the expression, <math>~I = I_\mathrm{BT} a_1^2</math>.</li>
<li>Throughout [[User:Tohline/Appendix/References#EFE|EFE]], Chandrasekhar adopts a sign convention for the scalar gravitational potential that is opposite to the sign convention being used here.</li>
</ol>




{{LSU_HBook_footer}}
{{LSU_HBook_footer}}

Latest revision as of 22:18, 14 June 2020


Riemann S-type Ellipsoids

Whitworth's (1981) Isothermal Free-Energy Surface
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General Coefficient Expressions

As has been detailed in an accompanying chapter, the gravitational potential anywhere inside or on the surface, <math>~(a_1,a_2,a_3) ~\leftrightarrow~(a,b,c)</math>, of an homogeneous ellipsoid may be given analytically in terms of the following three coefficient expressions:

<math> ~A_1 </math>

<math> ~= </math>

<math>~2\biggl(\frac{b}{a}\biggr)\biggl(\frac{c}{a}\biggr) \biggl[ \frac{F(\theta,k) - E(\theta,k)}{k^2 \sin^3\theta} \biggr] \, , </math>

<math> ~A_3 </math>

<math> ~= </math>

<math> ~2\biggl(\frac{b}{a}\biggr) \biggl[ \frac{(b/a) \sin\theta - (c/a)E(\theta,k)}{(1-k^2) \sin^3\theta} \biggr] \, , </math>

<math> ~A_2 </math>

<math> ~= </math>

<math>~2 - (A_1+A_3) \, ,</math>

where, <math>~F(\theta,k)</math> and <math>~E(\theta,k)</math> are incomplete elliptic integrals of the first and second kind, respectively, with arguments,

<math>~\theta = \cos^{-1} \biggl(\frac{c}{a} \biggr)</math>

      and      

<math>~k = \biggl[\frac{1 - (b/a)^2}{1 - (c/a)^2} \biggr]^{1/2} \, .</math>

[ EFE, Chapter 3, §17, Eq. (32) ]


TEST (part 1)
Notation: Use <math>~\phi</math> in place of <math>~\theta</math>.
<math>~\frac{b}{a}</math> <math>~\frac{c}{a}</math> <math>~\phi</math> <math>~k</math> Numerical Recipes <math>~A_1</math> <math>~A_2</math> <math>~A_3</math>
(deg) (rad) (deg) (rad) <math>~F(\phi,k) </math> <math>~E(\phi,k) </math>
0.9 0.641 50.13357253 0.874995907 32.53852919 0.567904468 0.909025949 0.843118048 0.521450273 0.595131012 0.883418715


Equilibrium Conditions for Riemann S-type Ellipsoids

We begin this section by quoting from the first paragraph in §II, p. 892 of Chandrasekhar (1965). "The problem that is to be considered … is that of a homogeneous mass, rotating uniformly with an angular velocity <math>\vec\Omega_f</math>, with internal motions having a uniform vorticity <math>~\vec\zeta</math> in the direction of <math>~\Omega_f</math> and in the frame of reference rotating with the angular velocity <math>~\vec\Omega_f</math>." As did Chandrasekhar, we will find it useful to refer to the ratio of these highlighted frequencies as the key model parameter,

<math>~f</math>

<math>~\equiv</math>

<math>~\frac{\zeta}{\Omega_f} \, .</math>

Chandrasekhar (1965), p. 892, §II, Eq. (15)

Based on Virial Equilibrium

Pulling from Chapter 7 — specifically, §48 — of Chandrasekhar's EFE, we understand that the semi-axis ratios, <math>~(\tfrac{b}{a}, \tfrac{c}{a})</math> associated with Riemann S-type ellipsoids are given by the roots of the equation,

<math>~ \biggl[ \frac{a^2 b^2}{a^2 + b^2} \biggr] f \biggl( \frac{\Omega^2}{\pi G \rho} \biggr) </math>

<math>~=</math>

<math>~a^2 b^2 A_{12} - c^2 A_3 \, ,</math>

[ EFE, §48, Eq. (34) ]

and the associated value of the square of the equilibrium configuration's angular velocity is,

<math>~\biggl[ 1 + \frac{a^2 b^2 \cdot f^2}{(a^2 + b^2)^2} \biggr] \frac{\Omega^2}{\pi G \rho}</math>

<math>~=</math>

<math>~2B_{12} \, ,</math>

[ EFE, §48, Eq. (33) ]

where,

<math>~A_{12}</math>

<math>~\equiv</math>

<math>~-\frac{A_1-A_2}{(a^2 - b^2)} \, ,</math>

[ EFE, §21, Eq. (107) ]

<math>~B_{12}</math>

<math>~\equiv</math>

<math>~A_2 - a^2A_{12} \, .</math>

[ EFE, §21, Eq. (105) ]

(Notice that if we set <math>~f \rightarrow 0</math>, this pair of expressions simplifies to the pair we have provided in a separate discussion of the equilibrium conditions for Jacobi ellipsoids.) Following Chandrasekhar's lead and eliminating <math>~\Omega^2</math> between these two expressions, we obtain,

<math>~0</math>

<math>~=</math>

<math>~ \biggl[ \frac{a^2 b^2}{(a^2 + b^2)^2} \biggr] f^2 + \biggl[ \frac{2a^2 b^2 B_{12}}{c^2 A_3 - a^2 b^2 A_{12}} \biggr]\frac{f}{a^2 + b^2} + 1 \, . </math>

[ EFE, §48, Eq. (35) ]

For a given <math>~f</math>, this last expression determines the ratios of the axes of the ellipsoids that are compatible with equilibrium; and the value of <math>~\Omega^2</math>, that is to be associated with a particular solution of this last expression, then follows from either one of the first two expressions. For convenience of evaluation and for greater clarity, let's rewrite this last (quadratic) equation in the form,

<math>~0</math>

<math>~=</math>

<math>~ \alpha f^2 + \beta f + 1 \, , </math>

in which case the pair of solutions is,

<math>~f</math>

<math>~=</math>

<math>~ \frac{1}{2\alpha}\biggr\{ - \beta \pm \biggl[ \beta^2 - 4\alpha \biggr]^{1 / 2} \biggr\} \, ; </math>

and the corresponding values of the angular velocity (in units of [G ρ]½) are provided by the expression,

<math>~\omega \equiv \frac{\Omega}{\sqrt{G\rho}}</math>

<math>~=</math>

<math>~ \pm \biggl\{ 2 \pi B_{12} \biggl[ 1 + \alpha f^2 \biggr]^{-1} \biggr\}^{1 / 2} </math>

As an aid in determining both values of the parameter, <math>~f</math>, we note as well that,

<math>~f_+ \cdot f_-</math>

<math>~=</math>

<math>~ \frac{1}{\alpha} = \biggl[ \frac{a^2 + b^2}{ab}\biggr]^2 \, . </math>


TEST (part 2)
<math>~\frac{b}{a}</math> <math>~\frac{c}{a}</math> <math>~a^2 A_{12}</math> <math>~ B_{12}</math> <math>~\alpha \equiv \frac{(b/a)^2}{[ 1 + (b/a)^2]^2} </math> <math>~\beta \equiv \biggl[ \frac{2 B_{12}}{(c/b)^2 A_3 - a^2 A_{12}} \biggr]\frac{1}{1 + (b/a)^2} </math> Direct Adjoint
<math>~f </math> <math>~\omega = \frac{\Omega}{\sqrt{G\rho}} </math> <math>~f^\dagger </math> <math>~\omega^\dagger = \frac{\Omega^\dagger}{\sqrt{G\rho}} </math>
0.9 0.641 0.387793362 0.207337649 0.247245200 3.797483556 - 0.268008879 ± 1.131374734 -15.09117122 ± 0.150771618

Based on Detailed Force Balance

The Steady-State Condition

As has been pointed out in our introductory discussion of the Principal Governing Equations, quite generally we can write the

Eulerian Representation
of the Euler Equation
as viewed from a Rotating Reference Frame

<math>\biggl[\frac{\partial\vec{v}}{\partial t}\biggr]_\mathrm{rot} + ({\vec{v}}_\mathrm{rot}\cdot \nabla) {\vec{v}}_\mathrm{rot}= - \frac{1}{\rho} \nabla P - \nabla \biggl[\Phi_\mathrm{grav} - \frac{1}{2}|{\vec{\Omega}}_f \times \vec{x}|^2 \biggr] - 2{\vec{\Omega}}_f \times {\vec{v}}_\mathrm{rot} \, ,</math>

where, <math>~{\vec{\Omega}}_f </math> specifies the time-invariant rotation frequency of the frame and the orientation of the vector about which the frame spins. The condition for detailed force balance in a steady-state configuration is obtained by setting <math>~[\partial \vec{v}/\partial t]_\mathrm{rot} = 0</math>. If we furthermore make the substitution, <math>~\nabla H = \nabla P/\rho</math>, where <math>~H</math> is enthalpy — an equation of state relation that is appropriate for a barytropic system — we obtain,

<math>~({\vec{v}}_\mathrm{rot} \cdot \nabla ){\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~ - \nabla\biggl[ H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)\biggr] - 2{\vec{\Omega}}_f \times {\vec{v}}_\mathrm{rot} \, . </math>

Ou(2006), p. 550, §2, Eq. (4)

Adopted Velocity Flow-Field

As Ou(2006) has pointed out [text that is taken directly from that publication appears here in an orange-colored font], the velocity field of a Riemann S-type ellipsoid as viewed from a frame rotating with angular velocity <math>~{\vec{\Omega}}_f = \boldsymbol{\hat{k}} \Omega_f</math> takes the following form:

<math>~{\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~\lambda \biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \biggl(\frac{b}{a}\biggr)x \biggr] \, ,</math>

Ou(2006), p. 550, §2, Eq. (3)


where <math>~\lambda</math> is a constant that determines the magnitude of the internal motion of the fluid, and the origin of the x-y coordinate system is at the center of the ellipsoid. This velocity field <math>~{\vec{v}}_\mathrm{rot}</math> is designed so that velocity vectors everywhere are always aligned with elliptical stream lines by demanding that they be tangent to the equi-effective-potential contours, which are concentric ellipses.

Plugging Ou's expression for <math>~{\vec{v}}_\mathrm{rot}</math> into the expression on the left-hand side of the steady-state Euler equation, we see that for Riemann S-type ellipsoids,

<math>~({\vec{v}}_\mathrm{rot} \cdot \nabla){\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~ \biggl[ \lambda\biggl(\frac{a}{b}\biggr)y \frac{\partial}{\partial x} - \lambda\biggl(\frac{b}{a}\biggr)x \frac{\partial}{\partial y} \biggr] \biggl[\boldsymbol{\hat{\imath}}\lambda\biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \lambda\biggl( \frac{b}{a}\biggr)x \biggr]</math>

 

<math>~=</math>

<math>~ - \boldsymbol{\hat{\jmath}} \biggl[ \lambda\biggl(\frac{a}{b}\biggr)y\biggr] \frac{\partial}{\partial x} \biggl[ \lambda\biggl( \frac{b}{a}\biggr)x \biggr] - \boldsymbol{\hat{\imath}} \biggl[ \lambda\biggl(\frac{b}{a}\biggr)x\biggr] \frac{\partial}{\partial y} \biggl[\lambda\biggl(\frac{a}{b}\biggr)y \biggr] </math>

 

<math>~=</math>

<math>~ -\lambda^2\biggl[ \boldsymbol{\hat{\imath}} x + \boldsymbol{\hat{\jmath}} y \biggr] = -\nabla\biggl[\frac{1}{2}\lambda^2(x^2 + y^2) \biggr] \, . </math>



Alternatively, from a separate discussion of vector identities we realize that,

<math> (\vec{v}\cdot\nabla)\vec{v} = \frac{1}{2}\nabla(\vec{v}\cdot \vec{v}) + \vec{\zeta}\times \vec{v} , </math>

where, <math>\vec\zeta \equiv \nabla\times\vec{v}</math> is the fluid vorticity. Plugging in Ou's expression for <math>~{\vec{v}}_\mathrm{rot}</math>, we find that …

<math>~\vec{\zeta} = \nabla\times {\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~-\boldsymbol{\hat{k}} \lambda \biggl[ \frac{b}{a} + \frac{a}{b} \biggr] \, ;</math>

Ou(2006), p. 551, §2, Eq. (17)

<math>~\vec{\zeta} \times {\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~-\lambda^2\biggl[\boldsymbol{\hat{\jmath}} \biggl(1 + \frac{a^2}{b^2}\biggr)y + \boldsymbol{\hat{\imath}} \biggl(1 + \frac{b^2}{a^2}\biggr)x \biggr] \, ; </math>     and,

<math>~\frac{1}{2}\nabla( {\vec{v}}_\mathrm{rot} \cdot {\vec{v}}_\mathrm{rot} )</math>

<math>~=</math>

<math>~\lambda^2\biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{b}{a}\biggr)^2x + \boldsymbol{\hat{\jmath}} \biggl(\frac{a}{b}\biggr)^2y \biggr] \, .</math>

Hence, we again appreciate that, for Riemann S-type ellipsoids,

<math>~( {\vec{v}}_\mathrm{rot} \cdot \nabla){\vec{v}}_\mathrm{rot} </math>

<math>~=</math>

<math>~-\lambda^2\biggl[ \boldsymbol{\hat{\imath}} x + \boldsymbol{\hat{\jmath}} y \biggr] </math>

<math>~=</math>

<math>~-\nabla\biggl[\frac{1}{2}\lambda^2(x^2 + y^2) \biggr] \, .</math>


The steady-state Euler-equation specification therefore becomes,

<math>~-\nabla\biggl[\frac{1}{2} \lambda^2(x^2 + y^2) \biggr]</math>

<math>~=</math>

<math>~ - \nabla\biggl[ H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2)\biggr] - \nabla\biggl[\Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) \biggr] \, . </math>

Ou(2006), p. 550, §2, Eq. (5)

Hence, within the configuration the following Bernoulli's function must be uniform in space:

<math>~ H + \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2) - \frac{1}{2} \lambda^2(x^2 + y^2) + \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) </math>

<math>~=</math>

<math>~ C_B \, , </math>

Ou(2006), p. 550, §2, Eq. (6)

where <math>~C_B</math> is a constant. It is customary to define an effective potential which is the sum of the gravitational potential and the system's centrifugal potential (as viewed from the rotating frame), namely,

<math>~\Phi_\mathrm{eff} \equiv \Phi_\mathrm{grav} + \Psi</math>

<math>~=</math>

<math>~ \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2) - \frac{1}{2} \lambda^2(x^2 + y^2) + \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) \, , </math>

Ou(2006), p. 550, §2, Eq. (7)

in which case the statement of detailed force balance in Riemann S-type ellipsoids can be rewritten in the following deceptively simpler form:

<math>~H + \Phi_\mathrm{eff}</math>

<math>~=</math>

<math>~C_B \, .</math>

Ou(2006), p. 550, §2, Eq. (8)

Evaluation of the Gravitational Potential

Drawing from a separate discussion of the gravitational potential of homogeneous ellipsoids, we see that for Riemann S-type ellipsoids,

<math> ~\Phi_\mathrm{grav}(\vec{x}) = -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr], </math>

[ EFE, Chapter 3, Eq. (40)1,2 ]
[ BT87, Chapter 2, Table 2-2 ]

where, the normalization constant,

<math> ~I_\mathrm{BT} </math>

<math> ~= A_1 + A_2\biggl(\frac{b}{a}\biggr)^2+ A_3\biggl(\frac{c}{a}\biggr)^2 . </math>

[ EFE, Chapter 3, Eq. (22)1]
[ BT87, Chapter 2, Table 2-2 ]

Implied Parameter Values

So, at the surface of the ellipsoid (where the enthalpy H = 0) on each of its three principal axes, the equilibrium conditions demanded by the expression for detailed force balance become, respectively:

  1. On the x-axis, where (x, y, z) = (a, 0, 0):

    <math>~C_B</math>

    <math>~=</math>

    <math>~ -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_1 a^2 \biggr] - \frac{1}{2} \Omega_f^2(a^2 ) - \frac{1}{2} \lambda^2(a^2) + \Omega_f \lambda \biggl(\frac{b}{a}\cdot a^2 \biggr) </math>

    <math>~\Rightarrow ~~~2\biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT} \biggr]</math>

    <math>~=</math>

    <math>~ (2\pi G \rho) A_1 - \Omega_f^2 - \lambda^2 + 2\Omega_f \lambda \biggl(\frac{b}{a} \biggr) </math>

  2. On the y-axis, where (x, y, z) = (0, b, 0):

    <math>~C_B</math>

    <math>~=</math>

    <math>~ -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_2 b^2 \biggr] - \frac{1}{2} \Omega_f^2(b^2) - \frac{1}{2} \lambda^2(b^2) + \Omega_f \lambda \biggl(\frac{a}{b}\cdot b^2 \biggr) </math>

    <math>~\Rightarrow ~~~ 2\biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT} \biggr]</math>

    <math>~=</math>

    <math>~ (2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr) - \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr) - \lambda^2\biggl( \frac{b^2}{a^2} \biggr) + 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr) </math>

  3. On the z-axis, where (x, y, z) = (0, 0, c):

    <math>~C_B</math>

    <math>~=</math>

    <math>~ -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_3 c^2 \biggr] </math>

    <math>~\Rightarrow ~~~ 2 \biggl[ \frac{C_B}{a^2} + (\pi G\rho)I_\mathrm{BT}\biggr]</math>

    <math>~=</math>

    <math>~ (2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr) </math>

Using the result from "III" to replace the left-hand side of both relation "I" and relation "II", we find that,

<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>

<math>~=</math>

<math>~ (2\pi G \rho) A_1 - \Omega_f^2 - \lambda^2 + 2\Omega_f \lambda \biggl(\frac{b}{a} \biggr) \, , </math>

and,

<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>

<math>~=</math>

<math>~ (2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr) - \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr) - \lambda^2\biggl( \frac{b^2}{a^2} \biggr) + 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr) \, . </math>

Multiplying the first of these two expressions by <math>~(b/a)^2</math> then subtracting it from the second gives,

<math>~(2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr) - \biggl(\frac{b}{a}\biggr)^2 (2\pi G \rho) A_3 \biggl( \frac{c^2}{a^2}\biggr)</math>

<math>~=</math>

<math>~ (2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr) + 2\Omega_f \lambda \biggl(\frac{b}{a}\biggr) - \biggl(\frac{b}{a}\biggr)^2 \biggl[ (2\pi G \rho) A_1 + 2\Omega_f \lambda \biggl(\frac{b}{a} \biggr) \biggr] </math>

<math>~\Rightarrow ~~~ \frac{(\pi G \rho)c^2}{ab} \biggl[ A_3 a^2 - A_3 b^2 \biggr]</math>

<math>~=</math>

<math>~ (\pi G \rho) (A_2 - A_1) a b + \Omega_f \lambda a^2 - ab \biggl[ \Omega_f \lambda \biggl(\frac{b}{a} \biggr) \biggr] </math>

 

<math>~=</math>

<math>~ (\pi G \rho) (A_2 - A_1) a b + \Omega_f \lambda ( a^2 - b^2 ) </math>

<math>~\Rightarrow ~~~ \frac{\Omega_f \lambda}{\pi G \rho} </math>

<math>~=</math>

<math>~ \frac{1}{a b ( a^2 - b^2 )}\biggl[ A_3 ( a^2 - b^2 )c^2 - (A_2 - A_1) a^2 b^2 \biggr] \, . </math>

Alternatively, just subtracting the first expression from the second gives,

<math>~0</math>

<math>~=</math>

<math>~ (2\pi G \rho) A_2 \biggl( \frac{b^2}{a^2}\biggr) - \Omega_f^2 \biggl( \frac{b^2}{a^2} \biggr) - \lambda^2\biggl( \frac{b^2}{a^2} \biggr) - \biggl[ (2\pi G \rho) A_1 - \Omega_f^2 - \lambda^2 \biggr]</math>

 

<math>~=</math>

<math>~ (2\pi G \rho) \biggl[ A_2 \biggl( \frac{b^2}{a^2}\biggr) - A_1 \biggr] + \Omega_f^2 \biggl[1 - \frac{b^2}{a^2} \biggr] + \lambda^2 \biggl[1 - \frac{b^2}{a^2} \biggr]</math>

<math>~\Rightarrow ~~~ \frac{\Omega_f^2 + \lambda^2}{\pi G \rho} </math>

<math>~=</math>

<math>~ 2 \biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] \, . </math>

We can eliminate <math>~\lambda</math> between these last two expressions as follows: From the first of the two, we have

<math>~ \lambda </math>

<math>~=</math>

<math>~ \frac{1}{\Omega_f} \biggl\{ \frac{\pi G \rho}{a b ( a^2 - b^2 )}\biggl[ A_3 ( a^2 - b^2 )c^2 - (A_2 - A_1) a^2 b^2 \biggr] \biggr\} \, . </math>

Hence, the second gives,

<math>~\Omega_f^2 </math>

<math>~=</math>

<math>~ 2 (\pi G \rho)\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] - \lambda^2 </math>

 

<math>~=</math>

<math>~ 2 (\pi G \rho)\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] - \frac{1}{\Omega_f^2} \biggl\{ \frac{\pi G \rho}{a b ( a^2 - b^2 )}\biggl[ A_3 ( a^2 - b^2 )c^2 - (A_2 - A_1) a^2 b^2 \biggr] \biggr\}^2 </math>

<math>~\Rightarrow ~~~ 0</math>

<math>~=</math>

<math>~ \frac{\Omega_f^4}{(\pi G \rho)^2} - \frac{2\Omega_f^2}{(\pi G \rho)} \biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] + \biggl\{ \frac{1}{a b ( a^2 - b^2 )}\biggl[ A_3 ( a^2 - b^2 )c^2 - (A_2 - A_1) a^2 b^2 \biggr] \biggr\}^2 \, . </math>

This is a quadratic equation whose solution gives <math>~\Omega_f^2/(\pi G \rho)</math> and, in turn, <math>~\lambda^2/(\pi G \rho)</math>. Specifically for Direct configurations, we find that,

<math>~\frac{\Omega_f^2}{(\pi G \rho)}</math>

<math>~=</math>

<math>~\frac{1}{2} \biggl[M + \sqrt{ M^2 - 4N^2} \biggr] \, ,</math>

      and      

<math>~\frac{\lambda^2}{(\pi G \rho)}</math>

<math>~=</math>

<math>~\frac{1}{2} \biggl[M - \sqrt{ M^2 - 4N^2} \biggr] \, ,</math>

Ou(2006), p. 551, §2, Eqs. (15) & (16)

where,

<math>~M</math>

<math>~\equiv</math>

<math>~ 2\biggl[ A_1 - A_2 \biggl( \frac{b^2}{a^2}\biggr) \biggr]\biggl[ \frac{a^2}{a^2 - b^2} \biggr] \, ,</math>     and,

<math>~N</math>

<math>~\equiv</math>

<math>~ \frac{1}{a b ( a^2 - b^2 )}\biggl[ A_3 ( a^2 - b^2 )c^2 - (A_2 - A_1) a^2 b^2 \biggr] \, . </math>


TEST (part 3)
<math>~\frac{b}{a}</math> <math>~\frac{c}{a}</math> <math>~A_1</math> <math>~A_2</math> <math>~A_3</math> <math>~M</math> <math>~N</math> <math>~\frac{\Omega_f^2}{\pi G \rho}</math> <math>~\frac{\lambda^2}{\pi G \rho}</math> <math>~\frac{\Omega_f}{\sqrt{G \rho}}</math> <math>~\frac{\lambda}{\sqrt{G \rho}}</math>
0.9 0.641 0.521450273 0.595131012 0.883418715 0.414682903 0.054301271 0.407446048 0.007236855 1.131383892 0.150782130


The numerical values listed in the last two columns of this "part 3" test match the values listed above in "part 2" of our test for, respectively, <math>~\omega</math> and <math>~\omega^\dagger</math>.

Relate EFE to Ou(2006)

As we have already acknowledged, according to Ou (2006), at any coordinate position inside or on the surface of the ellipsoid, <math>~(x, y)</math>, the three components of the velocity as viewed from a frame of rotation that is spinning at the equilibrium configuration's frequency, <math>~\Omega_f</math>, are,

<math>~{\vec{v}}_\mathrm{rot}</math>

<math>~=</math>

<math>~\lambda \biggl( \frac{ay}{b} , - \frac{bx}{a} , 0 \biggr) \, ,</math>

where, <math>~\lambda</math> is an overall scale factor. But, according to §48 of EFE, we see that,

<math>~\vec{u}</math>

<math>~=</math>

<math>~\biggl( Q_1 y , Q_2 x , 0 \biggr) \, ,</math>

Chandrasekhar (1965), p. 892, §II, Eq. (9)

where,

<math>~Q_1</math>

<math>~\equiv</math>

<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>

      and,      

<math>~Q_2</math>

<math>~\equiv</math>

<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta \, ,</math>

Chandrasekhar (1965), p. 892, §II, Eq. (10)

and <math>~\zeta</math> is the scalar magnitude of the vorticity vector, <math>~\vec\zeta</math>. The transformation from EFE's notation to the one used by Ou is, then,

<math>~\lambda \biggl( \frac{a}{b} \biggr) </math>

<math>~=</math>

<math>~- \biggl[ \frac{a^2}{a^2 + b^2} \biggr]\zeta</math>

      and,      

<math>~- \lambda \biggl( \frac{b}{a} \biggr) </math>

<math>~=</math>

<math>~+ \biggl[ \frac{b^2}{a^2 + b^2} \biggr]\zeta </math>

<math>~\Rightarrow ~~~ \lambda </math>

<math>~=</math>

<math>~- \biggl[ \frac{a b}{a^2 + b^2} \biggr]\zeta = - \biggl[ \frac{b}{a} + \frac{a}{b} \biggr]^{-1} \zeta\, ,</math>

which, gratifyingly agrees with Ou's equation (17). It is worth noting as well that, when viewed from the inertial reference frame, the velocity field is,

<math>~\vec{v}</math>

<math>~=</math>

<math>~{\vec{v}}_\mathrm{rot} + \vec\Omega_f \times \vec{x} \, .</math>

Chandrasekhar (1965), p. 892, §II, Eq. (13)

Broken down into its Cartesian components, this is

<math>~\vec{v}</math>

<math>~=</math>

<math>~ \boldsymbol{\hat\imath} \biggl[\lambda \biggl( \frac{a}{b} \biggr) - \Omega_f \biggr]y + \boldsymbol{\hat\jmath} \biggl[- \lambda \biggl( \frac{b}{a} \biggr) + \Omega_f \biggr]x </math>

 

<math>~=</math>

<math>~ \boldsymbol{\hat\imath} \biggl[- \biggl( \frac{a b}{a^2 + b^2} \biggr)\zeta \biggl( \frac{a}{b} \biggr) - \Omega_f \biggr]y + \boldsymbol{\hat\jmath} \biggl[\biggl( \frac{a b}{a^2 + b^2} \biggr)\zeta\biggl( \frac{b}{a} \biggr) + \Omega_f \biggr]x </math>

 

<math>~=</math>

<math>~ -\boldsymbol{\hat\imath} \biggl[ \biggl( \frac{a^2}{a^2 + b^2} \biggr) f + 1 \biggr] \Omega_fy + \boldsymbol{\hat\jmath} \biggl[\biggl( \frac{b^2}{a^2 + b^2} \biggr) f + 1 \biggr] \Omega_fx \, . </math>

Chandrasekhar (1965), p. 892, §II, Eq. (14)

Summary

It is often useful to discuss the properties of Riemann S-type ellipsoids in the context of what we will refer to as the traditional "EFE Diagram" — a two-dimensional parameter space defined by the axis ratio ranges, 0 ≤ b/a ≤ 1 and 0 ≤ c/a ≤ 1. It is useful to appreciate at the outset, for example, that Riemann S-type ellipsoids only populate a subset of the EFE Diagram's entire parameter space. More specifically, they all lie between or on the two (self-adjoint) curves marked "X = -1" and "X = +1" in the EFE Diagram that is shown here, on the right. Keeping this in mind, we summarize here a sequence of steps that should be taken in order to construct and thereby quantitatively detail all of the physical properties that are associated with any Riemann S-type ellipsoid that lies in this allowed region of the EFE Diagram.

Figure 1
EFE Diagram
Caption: See Figure 2, below
  1. Specify numerical values for any two of the three key parameters: <math>~b/a, c/a, f \equiv \zeta/\Omega_f</math>. The value of the third (unspecified) parameter can then be found by determining the root(s) of the virial-equilibrium-based expression,

    <math>~0</math>

    <math>~=</math>

    <math>~ \biggl[ \frac{a^2 b^2}{(a^2 + b^2)^2} \biggr] f^2 + \biggl[ \frac{2a^2 b^2 B_{12}}{c^2 A_3 - a^2 b^2 A_{12}} \biggr]\frac{f}{a^2 + b^2} + 1 \, . </math>

    [ EFE, §48, Eq. (35) ]
    1. If you specified the values of <math>~b/a</math> and <math>~c/a</math>, then values of the three parameters, <math>~A_1, A_2, A_3</math> — as well as the related parameters, <math>~A_{12}, B_{12}</math> — can be immediately determined from the above general coefficient expressions and related relations as long as you have an algorithm that can be used to evaluate incomplete elliptic integrals of the first and second kind. The governing virial-equilibrium-based expression then becomes a quadratic equation whose pair of roots give two physically viable values of the parameter, <math>~f</math>; we will refer to them as <math>~f_+</math> and <math>~f_-</math>
      NOTE: If the chosen pair of axis ratios places your configuration above the Jacobi/Dedekind sequence in the familiar "EFE Diagram," then the parameter, <math>~f</math>, will invariably be negative; if it is below the Jacobi/Dedekind sequence, <math>~f</math> will invariably be positive.
      NOTE as well: This is the method that we have used, below, in order to replicate various equilibrium configurations that have been studied by Ou (2006).
    2. If, instead, you specified the value of <math>~f</math> and (only) one of the ellipsoid's axis ratios, then an iterative numerical scheme — such as a Newton Raphson method — will need to be used in order to determine a physically viable (real) root of this nonlinear, virial-equilibrium-based expression. This root will provide the value of the equilibrium ellipsoid's other axis ratio.
      NOTE: The Jacobi/Dedelind sequence is determined in this manner by setting <math>~f = 0</math>, then determining what value of the c/a axis ratio is consistent with various selected values of 0 < b/a ≤ 1.
    3. If, as in step 1.B, only one value of the parameter, <math>~f</math>, is known, the other relevant value may be obtained from the relation,

      <math>~f_+ \cdot f_-</math>

      <math>~=</math>

      <math>~ \biggl[ \frac{a^2 + b^2}{ab}\biggr]^2 \, . </math>

      In either case, if <math>~|f_\pm | < 1</math> the model will be referred to as being a Jacobi-like — or, Direct — configuration because the magnitude of the configuration's spin frequency, <math>~|\Omega_f|</math>, is larger than the magnitude of the frequency, <math>~|\zeta|</math>, that characterizes internal motions (vorticity). On the other hand, if <math>~|f_\pm | > 1</math> the model will be referred to as being a Dedekind-like — or, Adjoint — configuration because the internal motions dominate.
      NOTE: A so-called self-adjoint model sequence will arise when <math>~f_+ = f_-</math> for all values of the axis ratio, 0 < b/a ≤ 1. There are two such sequences, namely, when <math>~f_+ = f_- = (a^2 + b^2)/(ab)</math> — this is the curve labeled, "X =+1" in the EFE Diagram shown here on the right — or when <math>~f_+ = f_- = -(a^2 + b^2)/(ab)</math> — this is the curve labeled, "X = - 1. In the familiar EFE diagram, these curves intersect the Maclaurin sequence (where, b/a = 1) when, respectively, <math>~f_+ = +2</math> and <math>~f_+ = -2</math>.

  2. Once a consistently specified set of parameters, <math>~b/a, c/a</math> and <math>~f</math>, is known, the configuration's spin frequency may be straightforwardly obtained from another virial-equilibrium-based expression, namely,

    <math>~\frac{\Omega_f^2}{\pi G \rho}</math>

    <math>~=</math>

    <math>~2B_{12} \biggl[ 1 + \frac{a^2 b^2 \cdot f^2}{(a^2 + b^2)^2} \biggr]^{-1} \, .</math>

    [ EFE, §48, Eq. (33) ]
  3. Once a consistently specified pair of parameters, <math>~\Omega_f</math> and <math>~f</math>, is known, the configuration's vorticity can immediately be determined via the expression,

    <math>~\vec\zeta = \boldsymbol{\hat{k}} \zeta </math>

        where,    

    <math>~\zeta = (f \Omega_f) \, .</math>
  4. At every location inside a Riemann S-type ellipsoid, the fluid vorticity must be related to the underlying velocity field via the expression, <math>~\vec\zeta = \nabla \times {\vec{v}}_\mathrm{rot}</math>. In order for the vorticity to be uniform throughout the configuration — everywhere being represented by the vector, <math>~\vec\zeta = \boldsymbol{\hat{k}} \zeta</math> — we realize that the velocity field is properly described by the expression,

    <math>~{\vec{v}}_\mathrm{rot}</math>

    <math>~=</math>

    <math>~\lambda \biggl[ \boldsymbol{\hat{\imath}} \biggl(\frac{a}{b}\biggr)y - \boldsymbol{\hat{\jmath}} \biggl(\frac{b}{a}\biggr)x \biggr] \, ,</math>

          where,      

    <math>~\lambda</math>

    <math>~\equiv</math>

    <math>~- \biggl[ \frac{ab}{a^2 + b^2} \biggr] \zeta \, .</math>

    Ou(2006), p. 550, §2, Eqs. (3) & (17)

Models Examined by Ou (2006)

In §2 of Ou (2006), immediately after equation (6), we find the following declaration:   In direct configurations, ω > λ so the fluid motion is dominated by figure rotation; conversely, in an adjoint configuration, ω < λ so the fluid motion is dominated by internal motions.

His Tabulated Model Parameters

Table 1 (see below) lists a subset of the Riemann S-type ellipsoids that were studied by Ou (2006); properties of various so-called Direct configurations can be found in Ou's Table 1, while properties of various Adjoint configurations can be found in his Table 5. Each row of our Table 1 was constructed as follows:

  • The pair of axis ratios <math>~(\tfrac{b}{a}, \tfrac{c}{a} )</math> associated with one of Ou's (2006) uniform-density, incompressible <math>~(n=0)</math> ellipsoid models (columns 1 and 2 from Ou's Table 1) has been copied into columns 1 and 2 of our table.
  • Properties of Direct Configurations
    • The pair of parameter values <math>~(\omega_\mathrm{analytic}, \lambda_\mathrm{analytic})</math> that is required in order for this to be an equilibrium configuration — as specified by the above set of analytical expressions from EFE — is copied from, respectively, columns 11 and 13 of Ou's Table 1 into columns 3 and 4 of our table; in our table, the "analytic" subscript has been dropped from the column headings.
    • The value of the equilibrium configuration's vorticity, <math>~\zeta</math> — see column 5 of our table — has been determined from the expression,
      <math>~\zeta = - \biggl[ \frac{1 + (b/a)^2}{b/a} \biggr] \lambda \, .</math>
    • Column 6 of our table lists the value of the frequency ratio, <math>~f \equiv \zeta/\omega</math>.
  • Properties of Adjoint Configurations [in order to distinguish from Direct configuration properties, a superscript † has been attached to each parameter name] …
    • As listed in column 7 of our Table, the "spin" angular velocity of the adjoint equilibrium configuration has been determined from the vorticity of the direct configuration via the relation,
      <math>~\omega^\dagger = \zeta \biggl[\frac{b/a}{1 + (b/a)^2}\biggr] \, .</math>
    • As listed in column 10 of our Table, the ratio <math>~(f^\dagger)</math> of the vorticity to the angular velocity in the adjoint equilibrium configuration has been determined from the same ratio <math>~(f)</math> in the direct configuration via the relation,
      <math>~f^\dagger = \frac{1}{f} \biggl\{ \frac{[1 + (b/a)^2]^2}{(b/a)^2} \biggr\} \, .</math>
    • As indicated, the value of the vorticity in the adjoint equilibrium configuration (column 9 of our table) has been determined from a product of <math>~\omega^\dagger</math> and <math>~f^\dagger</math>.
    • As listed in column 8 of our table, the value of the parameter, <math>~\lambda^\dagger</math>, has been determined from the vorticity in the adjoint equilibrium configuration via the relation,
      <math>~\lambda^\dagger = -~ \zeta^\dagger \biggl[ \frac{b}{a} + \frac{a}{b}\biggr]^{-1} \, .</math>

Table 1:   Example Riemann S-type Ellipsoids
[Cells with a pink background contain numbers copied directly from Table 1 of Ou (2006)]
[Cells with a yellow background contain numbers drawn from Table IV (p. 103) of EFE]

<math>~\frac{b}{a}</math> <math>~\frac{c}{a}</math>

Properties of
Direct Configurations

Properties of
Adjoint Configurations

<math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math> <math>~\lambda</math> <math>~\zeta </math> <math>~f \equiv \frac{\zeta}{\omega}</math> <math>~\omega^\dagger </math> <math>~\lambda^\dagger </math> <math>~\zeta^\dagger = \omega^\dagger f^\dagger</math> <math>~f^\dagger </math>
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
0.90 0.795 1.14704 0.43181 -0.86842 -0.75709 -0.43181 -1.14704 +2.30682 -5.3422
0.641 1.13137 0.15077 - 0.30322 - 0.26801 - 0.15077 -1.13137 2.27531 - 15.0913
0.590 1.10661 0.06406 -0.12883 -0.11642 -0.06406 -1.10661 +2.22552 -34.7411
0.564 1.09034 0.02033 -0.04089 -0.03750 -0.02033 -1.09034 +2.19279 -107.86
0.538 1.07148 - 0.02324 +0.04674 +0.04362 +0.02324 - 1.07148 +2.15487 +92.722
0.487 1.02639 - 0.10880 +0.21881 +0.21318 +0.10880 -1.02639 +2.06418 +18.972
0.333 0.79257 - 0.39224 +0.78884 +0.99529 +0.39224 -0.79257 +1.59395 +4.06370
0.28 0.256 0.80944 0.03668 -0.14127 -0.17453 -0.03668 -0.80944 +3.11750 -84.992
0.245083 0.796512a 0.0 0.0 0.0 0.0 <math>~\infty</math>
0.231 0.77651 - 0.04714 +0.18156 +0.23381 +0.04714 -0.77651 +2.99067 +63.442
0.205 0.72853 - 0.13511 +0.52037 +0.71427 +0.13511 -0.72853 +2.80588 +20.7674

aAccording to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.


Our Parameter Determinations

The parameter values that have been posted above in our Table 1 are typically given with five digits of precision. This is because, as explained, the values were determined from the analytically determined values, <math>~\omega_\mathrm{analytic}</math> and <math>~\lambda_\mathrm{analytic}</math>, that were provided by Ou (2006) with only five digit accuracy. Our Table 2 (shown immediately below) provides values of this same set of model parameters to better than eleven digits accuracy. We calculated these parameter values by following the steps detailed in earlier subsections of this chapter and, as a foundation, using double-precision versions of Numerical Recipes algorithms to evaluate the special functions, <math>~F(\phi,k)</math> and <math>~E(\phi,k)</math>. As an example, the above pair of brief tables titled, TEST (part 1) and TEST (part 2) detail all of the intermediate steps that were used in order to determine the high-precision parameter values specifically for the model having the axis-ratio pair <math>~(0.9,0.641)</math>. This table of higher precision parameter values was primarily generated in order to convince ourselves that we understood from first principles how to accurately determine the properties of Riemann S-type ellipsoids; the lower-precision parameter values that we derived from Ou's work provided a handy means of cross-checking these "first principles" determinations.

In generating our Table 2, we wondered what the approriate signs were of the various model parameters — especially when part of our objective is to distinguish between direct and adjunct configurations. We took the following approach: First we decided that the spin frequency of every direct configuration should be positive. (Evidently, Ou made this same choice.)

Table 2:   Example Riemann S-type Ellipsoids (double-precision evaluation)

<math>~\frac{b}{a}</math> <math>~\frac{c}{a}</math>

Properties of
Direct Configurations

Properties of
Adjoint Configurations

<math>~\omega = \frac{\Omega}{\sqrt{G \rho}}</math> <math>~\lambda</math> <math>~\zeta </math> <math>~f \equiv \frac{\zeta}{\Omega}</math> <math>~\omega^\dagger </math> <math>~\lambda^\dagger </math> <math>~\zeta^\dagger = \omega^\dagger f^\dagger</math> <math>~f^\dagger </math>
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
0.90 0.795 +1.147036091720 +0.431809451699 -0.868416786194 -0.757096320116 -0.431809460593 -1.147036104571 +2.306817054749 -5.342210487323
0.641 +1.131374738327 +0.150771621841 -0.303218483925 -0.268008886644 -0.150771621877 -1.131374730590 +2.275320291519 -15.091170863305
0.590 +1.106612583610 +0.064060198174 -0.128832176328 -0.116420305902 -0.064060197762 -1.106612576964 +2.225520849228 -34.741086358509
0.564 +1.090339840378 +0.020334563779 -0.040895067155 -0.037506716440 -0.020334563809 -1.090339837153 +2.192794561386 -107.8358300897
0.538 +1.071485625744 -0.023236834336 +0.046731855720 +0.043614077664 +0.023236835120 -1.071485656401 +2.154876708984 +92.735376233270
0.487 +1.026387311947 -0.108799837242 +0.218808561563 +0.213183225210 +0.108799835209 -1.026387320039 +2.064178943634 +18.972261524065
0.333 +0.792566980901 -0.392440787995 +0.789242029190 +0.995804846843 +0.392440793882 -0.792566979129 +1.593940258026 +4.061606964516
0.74 0.692 +1.132148956838 +0.385991660900 -0.807244181633 -0.713019398562 -0.385991654519 -1.132148989537 2.367721319199 -6.134125500116
0.41 0.385 +0.971082162758 +0.141593941719 -0.403404593468 -0.415417564427 -0.141593939418 -0.971082191477 2.766636848450 -19.539231537777
0.333 +0.929630138695 +0.003311666790 -0.009435019456 -0.010149218281 -0.003311666699 -0.929630099681 +2.648538827896 -799.7601146950
0.28 0.256 +0.809436834686 +0.036676037913 -0.141255140305 -0.174510396110 -0.036676038521 -0.809436833116 +3.117488145828 -85.000678306244
0.245083 0.796512a 0.0 0.0 0.0 0.0 <math>~\infty</math>
0.231 +0.776514825339 -0.047142035397 +0.181564182043 +0.233819345828 +0.047142037070 -0.776514835457 +2.990691423416 +63.440011724689
0.205 +0.728526018042 -0.135108121071 +0.520359277725 +0.714263156392 +0.135108125079 -0.728526039364 +2.805866003036 +20.767558718483

aAccording to Table IV (p. 103) of EFE, the square of the angular velocity of this Jacobi ellipsoid is, <math>~\Omega^2/(\pi G\rho) = 0.201946</math>; from this value, we find that, <math>~\omega = \sqrt{\pi} \cdot \sqrt{0.201946} = 0.796512</math>.

 

Figure 2:  EFE Diagram

In the context of our broad discussion of ellipsoidal figures of equilibrium, the label "EFE Diagram" refers to a two-dimensional parameter space defined by the pair of axis ratios (b/a, c/a), usually covering the ranges, 0 ≤ b/a ≤ 1 and 0 ≤ c/a ≤ 1. The classic/original version of this diagram appears as Figure 2 on p. 902 of S. Chandrasekhar (1965, ApJ, vol. 142, pp. 890-921); a somewhat less cluttered version appears on p. 147 of Chandrasekhar's [EFE].

The version of the EFE Diagram shown here, on the left, highlights four model sequences, all of which also can be found in the original version:

  • Jacobi sequence — the smooth curve that runs through the set of small, dark-blue, diamond-shaped markers; the data identifying the location of these markers have been drawn from §39, Table IV of [EFE]. The small red circular markers lie along this same sequence; their locations are taken from our own determinations, as detailed in Table 2 of our accompanying discussion of Jacobi ellipsoids. All of the models along this sequence have <math>~f \equiv \zeta/\Omega_f = 0</math> and are therefore solid-body rotators, that is, there is no internal motion when the configuration is viewed from a frame that is rotating with frequency, <math>~\Omega_f</math>.
  • Dedekind sequence — a smooth curve that lies precisely on top of the Jacobi sequence. Each configuration along this sequence is adjoint to a model on the Jacobi sequence that shares its (b/a, c/a) axis-ratio pair. All ellipsoidal figures along this sequence have <math>~1/f = \Omega_f/\zeta = 0</math> and are therefore stationary as viewed from the inertial frame; the angular momentum of each configuration is stored in its internal motion (vorticity).
  • The X = -1 self-adjoint sequence — At every point along this sequence, the value of the key frequency ratio, <math>~\zeta/\Omega_f</math>, in the adjoint configuration <math>~(f_+)</math> is identical to the value of the frequency ratio in the direct configuration <math>~(f_-)</math>; specifically, <math>~f_+ = f_- = -(a^2+b^2)/(ab)</math>. The data identifying the location of the small, solid-black markers along this sequence have been drawn from §48, Table VI of [EFE].
  • The X = +1 self-adjoint sequence — At every point along this sequence, the value of the key frequency ratio, <math>~\zeta/\Omega_f</math>, in the adjoint configuration <math>~(f_+)</math> is identical to the value of the frequency ratio in the direct configuration <math>~(f_-)</math>; specifically, <math>~f_+ = f_- = +(a^2+b^2)/(ab)</math>. The data identifying the location of the small, solid-black markers along this sequence have been drawn from §48, Table VI of [EFE].

Riemann S-type ellipsoids all lie between or on the two (self-adjoint) curves marked "X = -1" and "X = +1" in the EFE Diagram. The yellow circular markers in the diagram shown here, on the left, identify four Riemann S-type ellipsoids that were examined by Ou (2006) and that we have also chosen to use as examples.

EFE Diagram identifying example models from Ou (2006)

Feeding a 3D Animation

Initial Thoughts

Let's examine the elliptical trajectory of a Lagrangian particle that is moving in the equatorial plane of a Riemann S-Type ellipsoid. As viewed in a frame that is spinning about the Z-axis at angular frequency, <math>~\Omega</math>, the trajectory is defined by,

<math> r^2 </math>

<math> ~= </math>

<math>~ \biggl(\frac{x}{a} \biggr)^2 + \biggl(\frac{y}{b}\biggr)^2 \, , </math>

where <math>~0 < r \le 1</math>. (The surface of the relevant ellipsoid is associated with the value, <math>~r=1</math>.)

Let's choose a pair of axis ratios — for example, <math>~b/a = 0.28</math> and <math>~c/a = 0.231</math> — then, from Table 1 of our above discussion, draw the associated value of either <math>~\lambda</math> or <math>~\zeta</math> that corresponds to the Jacobi-like equilibrium configuration — in this example, <math>~\lambda = -0.04714</math> and <math>~\zeta = +0.18156</math>. Then, for any point <math>~(x,y)</math> inside of the ellipsoid, the fluid's velocity components (as viewed from the rotating frame of reference) are,

<math> v_x = \frac{dx}{dt} = \lambda \biggl( \frac{ay}{b} \biggr) = -0.16836 ~y </math>

      and,      

<math>~ v_y = \frac{dy}{dt} = - \lambda \biggl( \frac{bx}{a} \biggr) = + 0.01320~x \, . </math>

Alternatively, we have,

<math> u_x = \frac{dx}{dt} = Q_1 y = - \biggl[ 1 + \frac{b^2}{a^2} \biggr]^{-1}\zeta ~y = -0.16836 ~y </math>

      and,      

<math>~ u_y = \frac{dy}{dt}= Q_2 x = + \biggl[ 1 + \frac{a^2}{b^2} \biggr]^{-1}\zeta ~x = + 0.01320~x \, . </math>

Now, each Lagrangian fluid element's motion is oscillatory in both the <math>~x</math> and <math>~y</math> coordinate directions. So let's see how this plays out. Suppose,

<math> x = x_\mathrm{max} \cos(\varphi t) </math>

      and,      

<math>~ y = y_\mathrm{max} \sin(\varphi t) \, . </math>

Then,

<math> \frac{dx}{dt} = - x_\mathrm{max}\varphi \sin(\varphi t) = - \biggl( \frac{x_\mathrm{max}}{y_\mathrm{max}}\biggr) \varphi y = - \varphi \biggl(\frac{ay}{b}\biggr) </math>

      and,      

<math>~ \frac{dy}{dt} = y_\mathrm{max} \varphi \cos(\varphi t) = + \biggl( \frac{y_\mathrm{max}}{x_\mathrm{max}}\biggr) \varphi x = + \varphi \biggl(\frac{bx}{a}\biggr) \, . </math>

Hence our functional representation of the time-dependent behavior of both <math>~x</math> and <math>~y</math> works perfectly if, for each orbit inside of or on the surface of the configuration, we set <math>~\varphi = - \lambda</math> and if the ratio <math>~y_\mathrm{max}/x_\mathrm{max} = (b/a)</math>. Hooray!

Preferred Normalizations

Let's do this again, assuming that <math>~x</math> and <math>~y</math> both have units of length and that <math>~t</math> has the unit of time. Then, let's use <math>~a</math> to normalize lengths and use <math>~(\pi G \rho)^{-1 / 2}</math> to normalize time. We therefore have,

<math> \frac{x}{a} = \biggl(\frac{ x_\mathrm{max} }{a}\biggr) \cos\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}} \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr] </math>

      and,      

<math>~ \frac{y}{a} = \biggl(\frac{ y_\mathrm{max} }{a}\biggr) \sin\biggl[ \frac{\varphi}{(\pi G \rho)^{1 / 2}} \cdot \frac{t}{(\pi G \rho)^{-1 / 2}} \biggr] \, . </math>


NOTE:   When implementing in an xml-based COLLADA (3D animation) file, we associate <math>~\mathrm{TIME} = 4</math> with <math>~t \cdot (\pi G \rho)^{1 / 2} = 2\pi</math>. Hence we can everywhere replace <math>~t \cdot (\pi G \rho)^{1 / 2}</math> with (in radians) <math>~(\pi/2)\cdot \mathrm{TIME}</math> or (in degrees) <math>~90 \cdot \mathrm{TIME}</math>.


This also means that, if <math>~\varphi/(\pi G \rho)^{1 / 2} = 1</math>, each Lagrangian fluid element will move through one complete orbit (as viewed from a frame that is rotating with the ellipsoidal figure) in the time it takes the hand of the wall-mounted clock to complete one cycle.

Next, let's normalize the velocities such that <math>~\rho</math> and the total mass, <math>~M</math>, are both assumed to be the same in every examined Riemann ellipsoid. In particular, we will normalize to,

<math>~v_0</math>

<math>~\equiv</math>

<math>~(abc)^{1 / 3}(\pi G \rho)^{1 / 2}</math>

<math>~=</math>

<math>~a(\pi G \rho)^{1 / 2} \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{1 / 3} \, ,</math>

in which case we have,

<math> \frac{1}{v_0} \cdot \frac{dx}{dt} = - \frac{\varphi}{(\pi G \rho)^{1 / 2} } \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr) </math>

      and,      

<math>~ \frac{1}{v_0} \cdot \frac{dy}{dt} = + \frac{\varphi}{(\pi G \rho)^{1 / 2} } \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{x}{a}\biggr) \, . </math>

Finally, setting, <math>~\varphi/(\pi G\rho)^{1 / 2} \rightarrow -\lambda_\mathrm{EFE}</math> means,

<math> V_x \equiv \frac{1}{v_0} \cdot \frac{dx}{dt} = \lambda_\mathrm{EFE} \biggl(\frac{a}{b}\biggr)\biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{y}{a}\biggr) </math>

      and,      

<math>~ V_y \equiv \frac{1}{v_0} \cdot \frac{dy}{dt} = - \lambda_\mathrm{EFE} \biggl(\frac{b}{a}\biggr) \biggl( \frac{b}{a}\cdot \frac{c}{a} \biggr)^{-1 / 3} \cdot \biggl(\frac{x}{a}\biggr) \, . </math>

Example Mach Surface

Let's try to plot the "Mach surface" for the example model, b41c385, referenced below. Its relevant parameter values are,

  • <math>~b/a = 0.41</math>
  • <math>~c/a = 0.385</math>
  • <math>~\lambda_\mathrm{EFE} = 0.079886</math>

Hence, if we set a = 1 then we have,

<math>~V_x</math> <math>=</math> <math>~(0.079886) \biggl(\frac{1}{0.41}\biggr)\biggl( 1.85034 \biggr) \cdot y</math>      and      <math>~V_y</math> <math>=</math> <math>~- (0.079886) \biggl(0.41\biggr) \biggl( 1.85034 \biggr) \cdot x</math>
  <math>=</math> <math>~0.3605 y</math>     <math>=</math> <math>~- 0.0606 x</math>

Borrowing from an accompanying discussion, we have the following example data set.

Direct
n Axisymmetric b41c385 Surface |V| = 0.1
x0 y0 y = 0.41 × y0 Vx Vy |V| factor x y
1 1.0000 0.0000 0.0000 0.0000 -0.0606 0.0606 --- --- ---
2 0.9921 -0.1253 -0.0514 -0.0185 -0.0601 0.0629 --- --- ---
3 0.9686 -0.2487 -0.1020 -0.0368 -0.0587 0.0693 --- --- ---
4 0.9298 -0.3681 -0.1509 -0.0544 -0.0563 0.0783 --- --- ---
5 0.8763 -0.4818 -0.1975 -0.0712 -0.0531 0.0888 --- --- ---
6 0.8090 -0.5878 -0.2410 -0.0869 -0.0490 0.0998 1.002 0.8090 -0.2410
7 0.7290 -0.6845 -0.2807 -0.1012 -0.0442 0.1104 0.9058 0.6603 -0.2543
8 0.6374 -0.7705 -0.3159 -0.1139 -0.0386 0.1203 0.8313 0.5298 -0.2626
9 0.5358 -0.8443 -0.3462 -0.1248 -0.0325 0.1290 0.7752 0.4153 -0.2684
10 0.4258 -0.9048 -0.3710 -0.1337 -0.0258 0.1362 0.7342 0.3126 -0.2724
11 0.3090 -0.9511 -0.3899 -0.1406 -0.0187 0.1418 0.7052 0.2179 -0.2750
12 0.1874 -0.9823 -0.4027 -0.1452 -0.0114 0.1456 0.6868 0.1287 -0.2766
13 0.0628 -0.9980 -0.4092 -0.1475 -0.0038 0.1476 0.6775 0.0425 -0.2772


In an accompanying discussion of axisymmetric configurations, we have recognized that, at any point inside the configuration, the square of the sound speed is given approximately by the enthalpy where,

<math>~ c^2 \sim H(x, y, z) </math>

<math>~=</math>

<math>~\frac{P(x, y, z)}{\rho} = C_B - \Phi_\mathrm{eff}(x, y, z) </math>

 

<math>~=</math>

<math>~ C_B - \biggl[ \Phi_\mathrm{grav} - \frac{1}{2} \Omega_f^2(x^2 + y^2) - \frac{1}{2} \lambda^2(x^2 + y^2) + \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) \biggr] </math>

 

<math>~=</math>

<math>~ C_B + \pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr] + \frac{1}{2} \Omega_f^2(x^2 + y^2) + \frac{1}{2} \lambda^2(x^2 + y^2) - \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) </math>

 

<math>~=</math>

<math>~ -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - A_3 c^2 \biggr] + \pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr] + \frac{1}{2} \Omega_f^2(x^2 + y^2) + \frac{1}{2} \lambda^2(x^2 + y^2) - \Omega_f \lambda \biggl(\frac{b}{a}x^2 + \frac{a}{b}y^2 \biggr) </math>

 

<math>~=</math>

<math>~ \pi G \rho \biggl[A_3 c^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr] + \frac{ (\Omega_f^2+\lambda^2) }{2} \biggl[ x^2 + y^2\biggr] - \Omega_f \lambda \biggl[ \biggl(\frac{b}{a}\biggr) x^2 + \biggl( \frac{a}{b} \biggr)y^2 \biggr] </math>

<math>~\Rightarrow~~~ \frac{c^2}{a^2 (\pi G\rho)}</math>

<math>~\sim</math>

<math>~ \frac{ (\Omega_f^2+\lambda^2) }{2(\pi G \rho)} \biggl[ \biggl(\frac{x}{a}\biggr)^2 + \biggl( \frac{y}{a}\biggr)^2\biggr] - \frac{\Omega_f \lambda}{(\pi G \rho)} \biggl[ \biggl(\frac{b}{a}\biggr) \biggl( \frac{x}{a}\biggr)^2 + \biggl( \frac{a}{b} \biggr) \biggl( \frac{y}{a}\biggr)^2 \biggr] - \biggl[A_1 \biggl( \frac{x}{a}\biggr)^2 + A_2 \biggl(\frac{y}{a}\biggr)^2 +A_3 \biggl( \frac{z^2 - c^2}{a^2}\biggr) \biggr] \, . </math>

Drawing from equation (7) of Ou (2006) and from a separate discussion of gravitational potential of homogeneous ellipsoids, we see that the effective potential is,

<math> ~\Phi_\mathrm{eff}(\vec{x})\equiv \Phi + \Psi = -\pi G \rho \biggl[ I_\mathrm{BT} a^2 - \biggl(A_1 x^2 + A_2 y^2 +A_3 z^2 \biggr) \biggr] + \omega\lambda \biggl( \frac{b}{a}x^2 + \frac{a}{b} y^2\biggr) - \frac{\omega^2}{2}\biggl( x^2 + y^2\biggr) -\frac{\lambda^2}{2}\biggl(x^2 + y^2\biggr) \, , </math>

where,

<math> ~I_\mathrm{BT} </math>

<math> ~\equiv </math>

<math> ~A_1 + A_2\biggl(\frac{b}{a}\biggr)^2+ A_3\biggl(\frac{c}{a}\biggr)^2 \, . </math>

Setting <math>~\pi G \rho = 1</math>, let's use the test case from above — that is, (b/a, c/a) = (0.9, 0.641) — and see if we get the same value of the Bernoulli constant on the surface at each of the three principal axes. First, let's set x = y = 0 and z = c. In this case <math>~I_\mathrm{BT} = 1.36658564</math> we find,

<math>~\Phi_\mathrm{eff}</math>

<math>~=</math>

<math>~\biggl[1.36658564 - 0.36298 \biggr] = 1.00350567 \, .</math>

Next, let's set y = z = 0 and x = 1. In this case,

<math>~\Phi_\mathrm{eff}</math>

<math>~=</math>

<math>~\biggl[1.36658564 - 0.52145027 \biggr] + 0.10151682 -0.64000 - 0.01136605 = 0.29518175 \, .</math>

S-Type Ellipsoid Example b41c385

Figure 1a Figure 1b

EFE Model b41c385

EFE Model b41c385


The EFE model that we chose to use in our first successful construction of a COLLADA-based, 3D and interactive animation had the following properties (model selected from the above table):

  • <math>~b/a = 0.41</math>
  • <math>~c/a = 0.385</math>
  • <math>~\Omega_\mathrm{EFE} = \omega/\sqrt\pi = 0.971082/\sqrt\pi = 0.547874</math>
  • <math>~\lambda_\mathrm{EFE} = 0.141594/\sqrt\pi = 0.079886</math>

Figure 1 displays a pair of still-frame images of this (purple) ellipsoidal configuration after the ellipsoid has completed precisely five (counter-clockwise) spin cycles. (The snapshots have been taken at the same point in time, but from two different "camera" viewing angles.) The cycle of the "wall mounted" clock is based on the fundamental, EFE-adopted frequency of [π G ρ]½. In the left-hand image (labeled Figure 1a), the time on the clock appears to be about 9:08. This means that as the ellipsoid has completed five spin cycles, the clock has completed approximately [9 + 8/60] ≈ 9.13 cycles. In other words, the ratio (ellipsoid-to-clock) of these two frequencies is,

<math>~\frac{\Omega_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>

<math>~\approx</math>

<math>~\frac{5}{9.13} = 0.548 \, .</math>

This matches the tabulated value of <math>~\Omega_\mathrm{EFE}</math> presented above. Now, let's examine the motion of an example Lagrangian fluid element, which has been marked in the 3D scene by a red "arrow" riding in the equatorial plane and along the surface of the (purple) ellipsoidal figure. At time zero, the fluid marker was placed at the end of the longest axis of the ellipsoid that was nearest the "wall clock"; then, as time progressed and the ellipsoidal figure turned counter-clockwise, the fluid marker moved clockwise and completed less than one full "orbit" in the same time that the ellipsoidal figure completed five full spin cycles. In the right-hand image (labeled Figure 1b), we can see that relative to the ellipsoidal figure, the fluid marker has moved through approximately three-quarters of its assigned elliptical "orbit"; let's say, 73% of one full cycle. This means that the ratio of the Lagrangian fluid element's orbital frequency to the frequency of the wall-clock is,

<math>~\frac{\lambda_\mathrm{EFE}}{[\pi G \rho]^{1 / 2}}</math>

<math>~\approx</math>

<math>~\frac{0.73}{9.13} = 0.080 \, .</math>

This matches the tabulated value of <math>~\lambda_\mathrm{EFE}</math> presented above.


See Also

Chandrasekhar's Detailed Analysis

  • Bernhard Riemann (1876) Gesammelte Mathematische Werke und Wissenschaftlicher, especially Chapter X (p. 168) titled (something along the following line), "A Contribution to Research on Rotating Ellipsoidal Fluids"
  • S. Chandrasekhar (1965), ApJ, 142, 890 - 961. The Equilibrum and the Stability of the Riemann Ellipsoids. I. — This work is referenced as Paper XXV in EFE and focuses on S-type Riemann ellipsoids.
  • S. Chandrasekhar (1966), ApJ, 145, 842 - 877. The Equilibrum and the Stability of the Riemann Ellipsoids. II. — This work is referenced as Paper XXVIII in EFE and focuses on Riemann ellipsoids of Types I, II and III.

Finite-Amplitude Oscillations

  • L. F. Rossner (1967), ApJ, 149, 145. The Finite-Amplitude Oscillations of the Maclaurin Spheroids — This work is referenced as Paper XXXVIII in EFE.
  • M. Fujimoto (1968), ApJ, 152, 523. Gravitational Collapse of Rotating Gaseous Ellipsoids
  • T. T. Chia & S. Y. Pung (1995), Astrophysics and Space Science, 229, issue 2, 215 - 233. Effects of Variations of Parallel Angular Velocity and Vorticity on the Oscillations of Compressible Homogeneous Rotating Ellipsoids
  • T. T. Chia & S. Y. Pung (1997), Astrophysics and Space Science, 254, 269 - 294. Dynamical Behaviour of Compressible Homogeneous Uniformly Rotating Ellipsoids with Nonparallel Angular Velocity and Vorticity

In the Context of Galaxy Disks

Other

Footnotes

  1. In EFE this equation is written in terms of a variable <math>~I</math> instead of <math>~I_\mathrm{BT}</math> as defined here. The two variables are related to one another straightforwardly through the expression, <math>~I = I_\mathrm{BT} a_1^2</math>.
  2. Throughout EFE, Chandrasekhar adopts a sign convention for the scalar gravitational potential that is opposite to the sign convention being used here.


Whitworth's (1981) Isothermal Free-Energy Surface

© 2014 - 2021 by Joel E. Tohline
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Recommended citation:   Tohline, Joel E. (2021), The Structure, Stability, & Dynamics of Self-Gravitating Fluids, a (MediaWiki-based) Vistrails.org publication, https://www.vistrails.org/index.php/User:Tohline/citation