User:Tohline

Joel E. Tohline

A Fellow of the AAAS, Tohline has authored approximately one hundred articles in scientific journals and proceedings, primarily on problems related to complex fluid flows in astrophysical settings. His expertise in utilizing high-performance computers to accurately simulate the processes by which stars fom and to simulate catastrophic events that will give rise to bursts of gravitational radiation is recognized worldwide. Fifteen students have completed their doctoral dissertation research under his direction (an additional four under his co-direction) and, over the years, he has been a lead investigator on federal and state research or research-infrastructure grants totaling more than ten million dollars.

Retired at the end of the 2013 calendar year — after more than thirty-one years of service at Louisiana State University (LSU) — Tohline retains the titles of Director Emeritus of LSU's Center for Computation & Technology as well as Professor Emeritus in LSU's Department of Physics & Astronomy.

| Tohline's LSU Homepage | Resume ]

Note to Students and/or Potential Research Colleagues from Tohline: In retirement, I remain active in research. My two, quite expansive, ongoing efforts are briefly outlined in the paragraphs immediately following this biosketch. In the context of these two broadly defined research efforts, I am particularly interested in pursuing a number of well-defined theoretical or computational research projects that seem especially ripe for development at the present time. Some of these projects are listed below — each project title serving as a hypertext link to more descriptive, accompanying online material. In my judgment, most of these could be developed into doctoral-degree level research projects; at the very least they represent projects on which a graduate student (or advanced undergraduate) could hone her/his applied mathematics research skills. Having retired from LSU, I am not in a position to financially support or formally advise students who are in pursuit of a higher-education degree. I would nevertheless be interested in sharing my expertise — and, perhaps, developing a collaborative relationship — with individuals who are interested in pursuing answers to the questions posed by these identified projects.

Major Ongoing Effort #1: Online Textbook (under continual development)

The Structure, Stability and Dynamics of Self-Gravitating Fluids

• Preface: Much of our present, basic understanding of the structure, stability, and dynamical evolution of individual stars, short-period binary star systems, and the gaseous disks that are associated with numerous types of stellar systems (including galaxies) is derived from an examination of the behavior of a specific set of coupled, partial differential equations. These equations — most of which also are heavily utilized in studies of continuum flows in terrestrial environments — are thought to govern the underlying physics of all macroscopic "fluid" systems in astronomy. Although relatively simple in form, they prove to be very rich in nature... <more>

• Table of Contents
• Context
• Applications

Major Ongoing Effort #2: VisTrails Utilization

A brief accounting of my earliest experiences with VisTrails can be found on the page, titled Learning How to Use VisTrails, on my LSU website. While on sabbatical leave at the SCI Institute during the 2010 Spring semester, I became much more proficient in my use of this very versatile scientific visualization tool. Here are some examples:

1. A Customized Python Module for CFD Flow Analysis within VisTrails
2. Visualizing a Journal that can serve the Computational Sciences Community
3. January 2014: As I methodically march through various vtk (Visualization Took Kit) tools in an effort to gain a much better understanding of their capabilities, I will be documenting progress here.
4. Tutorial developed by Tohline: Simple Cube

Defined Research Projects

Stability of Bipolytropic Configurations

Using primarily analytic techniques, our objective is to evaluate the free energy of spherically symmetric, bipolytropic configurations (aka composite polytropes), then, use variations in the free energy function to identify equilibrium states (scalar virial theorem) and to assess the relative dynamical stability of the states.

• Early discussions with LSU graduate student, Kundan Kadam; see also construction of <math>~(n_c, n_e) = (0, 0)</math> bipolytrope
• Outline of Work Completed, to Date, on the free energy of pressure-truncated polytropes
• Relevant to …

	Schönberg-Chandrasekhar Mass
	Stellar Evolution from Main Sequence to Red Giant
	Bonnor-Ebert Spheres
	Origin of Planetary Nebulae

Compressible Analogs of Riemann Ellipsoids

We have known, for well over 100 years, that rapidly rotating, ellipsoidal-shaped equilibrium configurations can be constructed with a variety of different internal fluid velocity profiles — giving rise to Jacobi, Dedekind, or Riemann ellipsoids — if the fluid configuration has uniform density and is incompressible. Computational fluid-dynamic (CFD) simulations have demonstrated that dynamically stable compressible analogs of Riemann ellipsoids can be constructed, under certain conditions. Our desire is to develop a numerical technique, akin to the Hachisu self-consistent field (HSCF) technique, by which a wide range of such equilibrium configurations can be constructed a priori, without relying on CFD techniques.

• Shangli Ou developed an HSCF-type technique that successfully constructs approximate equilibrium configurations that are analogs of Riemann ellipsoids
• Some thoughts regarding how a more satisfactory velocity flow-field might be incorporated into Ou's technique in order to achieve this project objective
• Relevant to …

	The fission hypothesis for binary star formation
	Fission of liquid drops in spacelab experiments

Useful Links

• MediaWiki; Images and ImageMaps; Math; Interwiki Links
• Wiki Editing (Formatting Cheatsheet)
  • To set a redirect: #REDIRECT [[User:Tohline/page]]
  • To set internal link: [[User:Tohline/page | text]]
• Wiki Markup
• Character Entities; HTML Character Entities
• templates
• vtk READER file formats