Appendix/Ramblings/MyDoctoralStudents - Revision history

Jet53man at 23:49, 27 April 2022

2022-04-27T23:49:23Z

← Older revision		Revision as of 19:49, 27 April 2022
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	Over this time period, numerical simulations were carried out, to a large extent, on LSU's IBM main-frame computer. But, via [https://www.nsf.gov/awardsearch/showAward?AWD_ID=8818225&HistoricalAwards=false NSF funding], the group also was allocated time on Cray hardware at Minnesota's supercomputer center; Tohline and Williams both received training, for example, on Minnesota's newly acquired [https://en.wikipedia.org/wiki/Cray-2 Cray-2].		Over this time period, numerical simulations were carried out, to a large extent, on LSU's IBM main-frame computer. But, via [https://www.nsf.gov/awardsearch/showAward?AWD_ID=8818225&HistoricalAwards=false NSF funding], the group also was allocated time on Cray hardware at Minnesota's supercomputer center; Tohline and Williams both received training, for example, on Minnesota's newly acquired [https://en.wikipedia.org/wiki/Cray-2 Cray-2].

	<font color="red">Izumi Hachisu</font> (Kyoto University, Japan) joined the group in a postdoctoral research position for a couple of years. Drawing from his own research background, Hachisu provided us with a blueprint for developing a very efficient numerical algorithm for constructing rapidly rotating equilibrium configurations with spheroidal, toroidal, or binary-star geometric shapes — see our [[~~User:Tohline/~~AxisymmetricConfigurations/HSCF#Hachisu_Self-Consistent-Field_Technique\|relevant chapter discussion]]. Over the past several decades, this ''Hachisu Self-Consistent-Field'' technique has allowed us to construct a wide range of different self-gravitation configurations as initial states for stability analyses and for examining the nonlinear growth of unstable modes using computational fluid techniques.		<font color="red">Izumi Hachisu</font> (Kyoto University, Japan) joined the group in a postdoctoral research position for a couple of years. Drawing from his own research background, Hachisu provided us with a blueprint for developing a very efficient numerical algorithm for constructing rapidly rotating equilibrium configurations with spheroidal, toroidal, or binary-star geometric shapes — see our [[AxisymmetricConfigurations/HSCF#Hachisu_Self-Consistent-Field_Technique\|relevant chapter discussion]]. Over the past several decades, this ''Hachisu Self-Consistent-Field'' technique has allowed us to construct a wide range of different self-gravitation configurations as initial states for stability analyses and for examining the nonlinear growth of unstable modes using computational fluid techniques.
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Jet53man: /* Years 1994 - 2000 */

2022-04-27T23:38:56Z

Years 1994 - 2000

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	Our earlier CFD modeling of rapidly rotating polytropes showed that configurations that are sufficiently rapidly rotating will be subject to a dynamical bar-mode instability. <font color="red">John E. Cazes</font> showed that the nonlinear development of this instability usually results in the formation of a dynamically ''stable,'' self-gravitating structure that appears to be a compressible analog of a Riemann ellipsoid. Often, differential fluid flows inside the bar were supersonic and exhibited mild standing shocks near the ends of the bar, so the structure of each bar was necessarily expected to change on a secular time scale. After introducing a mechanism for slowly cooling the bar, Cazes observed that the bar became steadily more elongated and tended to develop a pair of off-axis density maxima. This ''suggested'' — but did not convincingly show — that as star-forming clouds slowly contract, they can smoothly transition from stable bar-like structures to binary protostellar configurations.		Our earlier CFD modeling of rapidly rotating polytropes showed that configurations that are sufficiently rapidly rotating will be subject to a dynamical bar-mode instability. <font color="red">John E. Cazes</font> showed that the nonlinear development of this instability usually results in the formation of a dynamically ''stable,'' self-gravitating structure that appears to be a compressible analog of a Riemann ellipsoid. Often, differential fluid flows inside the bar were supersonic and exhibited mild standing shocks near the ends of the bar, so the structure of each bar was necessarily expected to change on a secular time scale. After introducing a mechanism for slowly cooling the bar, Cazes observed that the bar became steadily more elongated and tended to develop a pair of off-axis density maxima. This ''suggested'' — but did not convincingly show — that as star-forming clouds slowly contract, they can smoothly transition from stable bar-like structures to binary protostellar configurations.

	In an effort to ascertain whether the results obtained from Woodward's earlier CFD-based examination of the stability of toroidal configurations were consistent with the results of linear stability analyses previously published by other groups, <font color="red">Saied W. Andalib</font> completed a project — in close collaboration with Christodoulou — titled, "A Survey of the Principal Modes of Nonaxisymmetric Instability in Self-Gravitating Accretion-Disk Models." Andalib also developed a technique for constructing 2D equilibrium structures of compressible and differentially rotating ''disks'' that exhibit nonlinear distortions in the azimuthal coordinate direction. (A very similar technique is described in the 1996 publication by [[~~User:Tohline/~~Apps/Korycansky_Papaloizou_1996#Korycansky_and_Papaloizou_.281996.29\|Korycansky & Papaloizou]].) The variety of model geometries that were obtained with this new tool helped us place in better context the range of distorted models that developed spontaneously during John Cazes' simulations.		In an effort to ascertain whether the results obtained from Woodward's earlier CFD-based examination of the stability of toroidal configurations were consistent with the results of linear stability analyses previously published by other groups, <font color="red">Saied W. Andalib</font> completed a project — in close collaboration with Christodoulou — titled, "A Survey of the Principal Modes of Nonaxisymmetric Instability in Self-Gravitating Accretion-Disk Models." Andalib also developed a technique for constructing 2D equilibrium structures of compressible and differentially rotating ''disks'' that exhibit nonlinear distortions in the azimuthal coordinate direction. (A very similar technique is described in the 1996 publication by [[Apps/Korycansky_Papaloizou_1996#Korycansky_and_Papaloizou_.281996.29\|Korycansky & Papaloizou]].) The variety of model geometries that were obtained with this new tool helped us place in better context the range of distorted models that developed spontaneously during John Cazes' simulations.

	Over this time period, we continued to receive NSF allocations of supercomputing time, but we shifted from the CTC to the [https://www.sdsc.edu San Diego Supercomputing Center (SDSC)] for two reasons: (1) It appeared to us that it would be relatively easy for us to migrate the parallel version of our CFD code — which had been developed using MasPar Fortran — to the SDSC's Cray T3D (then T3E) because PGHPF (Portland Group's High-Performance Fortran) was a supported compiler on the Cray platforms. (2) The SDSC's new ''Advanced Scientific Visualization Laboratory (Vislab)'' was providing access to visualization tools on its Silicon Graphics Onyx2, such as Alias\|Wavefront. At approximately the same time, a virtually identical computing environment was developed at the DoD's new [http://benchpub.powweb.com/GULFPORT03/resources/03.html Major Shared Resource Center (MSRC) in Stennis, MS]; after being introduced to the MSRC's managers by Warren N. Waggenspack Jr. (LSU, Mechanical Engineering), we also received an allocation of time on these computing resources via the [http://aspen.ucs.indiana.edu/pet/ DoD's Programming Environment & Training (PET) program].		Over this time period, we continued to receive NSF allocations of supercomputing time, but we shifted from the CTC to the [https://www.sdsc.edu San Diego Supercomputing Center (SDSC)] for two reasons: (1) It appeared to us that it would be relatively easy for us to migrate the parallel version of our CFD code — which had been developed using MasPar Fortran — to the SDSC's Cray T3D (then T3E) because PGHPF (Portland Group's High-Performance Fortran) was a supported compiler on the Cray platforms. (2) The SDSC's new ''Advanced Scientific Visualization Laboratory (Vislab)'' was providing access to visualization tools on its Silicon Graphics Onyx2, such as Alias\|Wavefront. At approximately the same time, a virtually identical computing environment was developed at the DoD's new [http://benchpub.powweb.com/GULFPORT03/resources/03.html Major Shared Resource Center (MSRC) in Stennis, MS]; after being introduced to the MSRC's managers by Warren N. Waggenspack Jr. (LSU, Mechanical Engineering), we also received an allocation of time on these computing resources via the [http://aspen.ucs.indiana.edu/pet/ DoD's Programming Environment & Training (PET) program].
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	<font color="red">Howard S. Cohl</font> made two key contributions to the development of our Poisson solver: (1) A parallel implementation of a data-transpose technique to facilitate, on our SIMD-architecture MasPar, fast execution of an iterative scheme to evaluate the Newtonian gravitational potential throughout the interior volume of the grid; and (2) a compact cylindrical Green's function (CCGF) expansion that much more effectively facilitates an accurate evaluation of potential values along the exterior boundary of our cylindrical-coordinate grid.		<font color="red">Howard S. Cohl</font> made two key contributions to the development of our Poisson solver: (1) A parallel implementation of a data-transpose technique to facilitate, on our SIMD-architecture MasPar, fast execution of an iterative scheme to evaluate the Newtonian gravitational potential throughout the interior volume of the grid; and (2) a compact cylindrical Green's function (CCGF) expansion that much more effectively facilitates an accurate evaluation of potential values along the exterior boundary of our cylindrical-coordinate grid.

	Comment from Tohline:  As has been detailed in an [[~~User:Tohline/~~Appendix/Ramblings/CCGF#Compact_Cylindrical_Green_Function_.28CCGF.29\|accompanying chapter on this CCGF paper]], over my professional career this has proven to be the publication with the most citations from research groups outside of the astrophysics community. Howard Cohl deserves full credit for the important discovery presented in this paper; I simply tagged along as his physics doctoral dissertation advisor and harshest skeptic.		Comment from Tohline:  As has been detailed in an [[Appendix/Ramblings/CCGF#Compact_Cylindrical_Green_Function_.28CCGF.29\|accompanying chapter on this CCGF paper]], over my professional career this has proven to be the publication with the most citations from research groups outside of the astrophysics community. Howard Cohl deserves full credit for the important discovery presented in this paper; I simply tagged along as his physics doctoral dissertation advisor and harshest skeptic.
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Jet53man: /* Preface */

2022-04-11T23:20:40Z

Preface

← Older revision		Revision as of 19:20, 11 April 2022
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	==Preface==		==Preface==
	Looking back, it seems clear to me that the technical book that has had the most influence on my research career has been [<b>[[~~User:Tohline/~~Appendix/References#EFE\|<font color="red">EFE</font>]]</b>], that is, Chandrasekhar's (originally, 1969) ''Ellipsoidal Figures of Equilibrium.'' Chandrasekhar evaluated the relative stability of a wide variety of astrophysically interesting (usually ''Newtonian'' self-gravitating), rotating equilibrium configurations by employing his own exceptional mathematical skills and those of his students — notably, Norman Lebovitz. When I entered graduate school at UC, Santa Cruz in 1974, [<b>[[~~User:Tohline/~~Appendix/References#EFE\|<font color="red">EFE</font>]]</b>] was the set of glasses through which most astronomers examined stability. Having access to only meager computing resources, Chandrasekhar's descriptions of the onset of instabilities, or evolution between nearly adjacent states, was usually limited to linear-amplitude deviations from equilibrium. From the beginning, I have been interested in using (steadily improving) computational resources to repeat, then extend the analyses found in [<b>[[~~User:Tohline/~~Appendix/References#EFE\|<font color="red">EFE</font>]]</b>] … (1) to configurations with non-homogeneous and compressible structures; and (2) into the nonlinear regime.		Looking back, it seems clear to me that the technical book that has had the most influence on my research career has been [<b>[[Appendix/References#EFE\|<font color="red">EFE</font>]]</b>], that is, Chandrasekhar's (originally, 1969) ''Ellipsoidal Figures of Equilibrium.'' Chandrasekhar evaluated the relative stability of a wide variety of astrophysically interesting (usually ''Newtonian'' self-gravitating), rotating equilibrium configurations by employing his own exceptional mathematical skills and those of his students — notably, Norman Lebovitz. When I entered graduate school at UC, Santa Cruz in 1974, [<b>[[Appendix/References#EFE\|<font color="red">EFE</font>]]</b>] was the set of glasses through which most astronomers examined stability. Having access to only meager computing resources, Chandrasekhar's descriptions of the onset of instabilities, or evolution between nearly adjacent states, was usually limited to linear-amplitude deviations from equilibrium. From the beginning, I have been interested in using (steadily improving) computational resources to repeat, then extend the analyses found in [<b>[[Appendix/References#EFE\|<font color="red">EFE</font>]]</b>] … (1) to configurations with non-homogeneous and compressible structures; and (2) into the nonlinear regime.

	The MediaWiki-formatted text that you are reading — titled, ''The Structure, Stability, & Dynamics of Self-Gravitating Fluids'' — is my attempt to explain in detail what has been learned as a result of our (and the broader astrophysics community's) extension of the foundation work presented in [<b>[[~~User:Tohline/~~Appendix/References#EFE\|<font color="red">EFE</font>]]</b>]. The chapters of this ever-developing book that, on any date, I consider ready for public consumption can be found on the MediaWiki page that I refer to as the [[~~User:Tohline/~~H_BookTiledMenu#Tiled_Menu\|Tiled Menu]]. The [[#Doctoral_Students_Tohline_Has_Advised\|graduate students who have come through my group]] over the years have made important contributions to the healthy development of this research field. The [[#Outline_of_Research_Activities\|''Outline of Research Activities'']] that is presented, below, highlights and summarizes these contributions.		The MediaWiki-formatted text that you are reading — titled, ''The Structure, Stability, & Dynamics of Self-Gravitating Fluids'' — is my attempt to explain in detail what has been learned as a result of our (and the broader astrophysics community's) extension of the foundation work presented in [<b>[[Appendix/References#EFE\|<font color="red">EFE</font>]]</b>]. The chapters of this ever-developing book that, on any date, I consider ready for public consumption can be found on the MediaWiki page that I refer to as the [[H_BookTiledMenu#Tiled_Menu\|Tiled Menu]]. The [[#Doctoral_Students_Tohline_Has_Advised\|graduate students who have come through my group]] over the years have made important contributions to the healthy development of this research field. The [[#Outline_of_Research_Activities\|''Outline of Research Activities'']] that is presented, below, highlights and summarizes these contributions.

	==Doctoral Students Tohline Has Advised==		==Doctoral Students Tohline Has Advised==

Jet53man: Created page with "FORCETOC =Chronology of Research Endeavors= ==Preface== Looking..."

2021-07-24T20:56:06Z

Created page with "__FORCETOC__   =Chronology of Research Endeavors= ==Preface== Looking..."

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Appendix/Ramblings/MyDoctoralStudents - Revision history

Jet53man at 23:49, 27 April 2022

Jet53man: /* Years 1994 - 2000 */

Jet53man: /* Preface */

Jet53man: Created page with "__FORCETOC__ =Chronology of Research Endeavors= ==Preface== Looking..."

Jet53man: Created page with "FORCETOC =Chronology of Research Endeavors= ==Preface== Looking..."