Difference between revisions of "User:Tohline/SSC/Virial/PolytropesSummary"

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(Begin writing summary chapter on the virial equilibrium of pressure-truncated polytropic spheres)
 
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The summary presented here has been drawn from our  
The summary presented here has been drawn from our  
[[User:Tohline/SSC/Virial/Polytropes#Virial_Equilibrium_of_Adiabatic_Spheres|accompanying detailed analysis of the structure of pressure-truncated polytropes]].
[[User:Tohline/SSC/Virial/Polytropes#Virial_Equilibrium_of_Adiabatic_Spheres|accompanying detailed analysis of the structure of pressure-truncated polytropes]].


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<div align="center">
[[File:AdabaticBoundedSpheres_Virial.jpg|thumb|300px|Equilibrium Adiabatic Pressure-Radius Diagram]]
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The variation with radius, <math>~\chi \equiv R/R_\mathrm{norm}</math>, of the normalized free energy, <math>~\mathfrak{G}^* \equiv \mathfrak{G}/E_\mathrm{norm}</math>, of pressure-truncated adiabatic spheres is described by the following algebraic function:
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'''Figure 4:''' <font color="darkblue">Equilibrium Adiabatic P-V Diagram </font>  
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The curves trace out the function,
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<math>
<math>
\Pi_a = (\chi^{4-3\gamma_g} - 1)/\chi^4 \, ,
\mathfrak{G}^* =  
-3\mathcal{A} \chi^{-1} -~ \frac{1}{(1-\gamma_g)} \mathcal{B} \chi^{3-3\gamma_g} +~ \mathcal{D}\chi^3 \, ,
</math>
</math>
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for six different values of <math>\gamma_g</math> (<math>2, ~5/3, ~7/5, ~6/5, ~1, ~2/3</math>, as labeled)  and show the dimensionless external pressure, <math>\Pi_a</math>, that is required to construct a nonrotating, self-gravitating, uniform density, adiabatic sphere with an equilibrium radius <math>\chi</math>.  The mathematical solution becomes unphysical wherever the pressure becomes negative.
where, <math>~\mathcal{A}</math>, <math>~\mathcal{B}</math>, and <math>~\mathcal{D}</math> are constants.


The solid red curve, drawn for the case <math>\gamma_g = 1</math>, is identical to the solid black (isothermal) curve displayed above in Figure 1.
The curves shown in the accompanying "pressure-radius" diagram trace out the function,
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<math>
[[File:AdabaticBoundedSpheres_Virial.jpg|450px|center|Equilibrium Adiabatic P-R Diagram]]
\Pi_\mathrm{ad} = (\chi_\mathrm{ad}^{4-3\gamma} - 1)/\chi_\mathrm{ad}^4 \, ,
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</math>
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for six different values of the adiabatic exponent, <math>~\gamma</math>, as labeled.  They show the dimensionless external pressure, <math>~\Pi_\mathrm{ad}\equiv P_e/P_\mathrm{ad}</math>, that is required to construct a nonrotating, self-gravitating, adiabatic sphere with a dimensionless equilibrium radius <math>~\chi_\mathrm{ad} \equiv R_\mathrm{eq}/R_\mathrm{ad}</math>.  The mathematical solution becomes unphysical wherever the pressure becomes negative.


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Revision as of 22:33, 9 October 2014


Virial Equilibrium of Adiabatic Spheres (Summary)

The summary presented here has been drawn from our accompanying detailed analysis of the structure of pressure-truncated polytropes.

Whitworth's (1981) Isothermal Free-Energy Surface
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Equilibrium Adiabatic Pressure-Radius Diagram

The variation with radius, <math>~\chi \equiv R/R_\mathrm{norm}</math>, of the normalized free energy, <math>~\mathfrak{G}^* \equiv \mathfrak{G}/E_\mathrm{norm}</math>, of pressure-truncated adiabatic spheres is described by the following algebraic function:

<math> \mathfrak{G}^* = -3\mathcal{A} \chi^{-1} -~ \frac{1}{(1-\gamma_g)} \mathcal{B} \chi^{3-3\gamma_g} +~ \mathcal{D}\chi^3 \, , </math>

where, <math>~\mathcal{A}</math>, <math>~\mathcal{B}</math>, and <math>~\mathcal{D}</math> are constants.

The curves shown in the accompanying "pressure-radius" diagram trace out the function,

<math> \Pi_\mathrm{ad} = (\chi_\mathrm{ad}^{4-3\gamma} - 1)/\chi_\mathrm{ad}^4 \, , </math>

for six different values of the adiabatic exponent, <math>~\gamma</math>, as labeled. They show the dimensionless external pressure, <math>~\Pi_\mathrm{ad}\equiv P_e/P_\mathrm{ad}</math>, that is required to construct a nonrotating, self-gravitating, adiabatic sphere with a dimensionless equilibrium radius <math>~\chi_\mathrm{ad} \equiv R_\mathrm{eq}/R_\mathrm{ad}</math>. The mathematical solution becomes unphysical wherever the pressure becomes negative.

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