Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Volume 67, Number 19
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session T01: Minisymposia: Astrophysical Turbulence: Current Understanding and Modeling Challenges |
Hide Abstracts |
Chair: Daniel Livescu, LANL; Christopher Lee Fryer, LANL Room: Sagamore 123 |
Monday, November 21, 2022 4:10PM - 4:36PM |
T01.00001: Interstellar Turbulent Flows: Decoupled, Multiphase, and Multiphysics Invited Speaker: Mordecai-Mark Mac Low Interstellar gas typically has Reynolds number far exceeding unity, as dynamic viscosities are 10-4 to 102 g/(cm sec), while typical length scales exceed parsecs (3 x 1018 cm), typical velocities are 10 to 100 km/s, and typical densities are 10-25 to 10-22 g cm-3. Thus, nearly all interstellar flows will develop turbulent structure. However, interstellar gas is extremely compressible, has multiple thermal phases, is coupled to magnetic fields, and is strongly influenced by gravity. Flows in the gas are driven both by gravity at all scales, and point-source stellar feedback (supernova explosions, ionizing radiation, and stellar outflows). In this talk I explore the implications of the deviation of interstellar gas from ideal incompressible turbulence models, with a focus on star formation in galaxies and the growth of magnetic fields due to the small-scale dynamo. In the case of gravitational collapse to star formation, the multiphase nature of the interstellar gas prevents large-scale turbulent flows driven by supernovae and other stellar feedback from effectively coupling to the turbulent flows driven by gravitational collapse within the dense, cold clouds where stars form. Only in extremely high surface density galaxies characteristic of the early universe are the large-scale flows also driven by gravity. In all cases, the density structure of star forming regions is ultimately determned by gravity despite the presence of turbulent flow. In the case of the small-scale dynamo, the thermal phase structure leads to decoupling of dynamos in different phases that grow at rates determined by the local sound speed. When there is a large filling factor of hot gas with high sound speed, magnetic energy growth occurs fastest there despite its low inertia. At other times, slower growth rates in cold or warm gas can still lead to substantial growth of total magnetic energy. |
Monday, November 21, 2022 4:36PM - 5:02PM |
T01.00002: How turbulence informs and impacts our interpretations of astrophysical observations Invited Speaker: Daniel Patnaude Turbulence is a natural and expected phenomenon in astrophysical systems. It is manifested at all scales, from pulsar outflows, to supernova ejecta, and even to the largest scales of the circum- and intergalactic medium. In this talk, I will discuss the role that astrophysical turbulence has in impacting what we observe in astrophysical phenomena, and how it impacts our interpretation of observational data. I will discuss observational diagnostics which can inform us on the level of turbulence in an astrophysical flow, and how this information can guide detailed numerical models. |
Monday, November 21, 2022 5:02PM - 5:28PM |
T01.00003: Turbulence in Neutron Star Mergers Invited Speaker: David Radice What is the nature of dense matter in neutron stars? Where are elements heavier than iron formed in the Universe? What is the engine powering short gamma-ray busts? Gravitational wave and electromagnetic observations of merging neutron stars hold the key to answer these and other important open questions in astrophysics. However, turning observational data into answers require sophisticated theoretical models. This is challenging because of the rich physics and the complex turbulent flows characterizing these phenomena. This talk will review the current understanding of relativistic (magneto-)hydrodynamics turbulence in neutron star mergers and its impact on their multimessenger signal. I will discuss the simulation techniques used to model the postmerger phase of binary neutron star mergers, highlighting recent progress and open problems. |
Monday, November 21, 2022 5:28PM - 5:54PM |
T01.00004: Modeling Astrophysics Reactions in Turbulent Environments Invited Speaker: Michael Zingale Nuclear reactions are the dominant energy source that drive stellar evolution and explosions. Convection and burning front propagation occurs at high Reynolds number where turbulence reigns and potentially impacts the character of the burning. In this talk, I will describe some astrophysical environments where turbulent burning takes place, including thermonuclear supernova and massive star evolution, and discuss the challenges in performing accurate simulations of these processes. |
Monday, November 21, 2022 5:54PM - 6:20PM |
T01.00005: On-the-fly reduced-order modeling of turbulent flames in Type Ia supernovae Invited Speaker: Arash G Nouri A review is conducted of the state of progress in physical modeling and computational simulations of turbulent flames as pertaining to Type Ia supernovae. The continuum-level governing equations are simplified with various assumptions, to make a case for a more systematic inclusion of turbulence-reaction interactions for future investigations. We also report on recent progress made in using time-dependent subspaces for reduced-order modeling (TDB-ROM) of turbulent reacting flows with large number of isotopes. Unlike data-driven reduced-order modeling techniques, e.g. principal component analysis, TDB-ROM does not require any offline data generation and, as a result, TDB-ROM can adapt on-the-fly to changes in problem dynamics. First, a skeletal kinetics reduction technique is presented, in which the most important reactions and isotopes are detected in a detailed reaction network by on-the-fly reduced-order modeling of sensitivities. The generated skeletal models are then implemented in multi-dimensional simulations. The method is demonstrated for carbon-oxygen combustion under Type Ia conditions. Extensions of TDB-ROM in evolving isotopes transport equations are also discussed. This application of TDB-ROM decreases the computation and book-keeping costs by ns/r, where ns and r are the number of isotopes and reduction size, respectively. |
Monday, November 21, 2022 6:20PM - 6:46PM |
T01.00006: Astrophysical perspectives on relativistic turbulence Invited Speaker: Jonathan Zrake I will talk about relativistic turbulence. Turbulence is ubiquitious in astrophysical settings. In high-energy sources like relativistic jets, and also nearby compact objects, turbulent flows can become relativistic in nature. Either because the random fluid motions are close to the speed of light, or the gas is hot and the speed of sound is relativistic, or because plasma is strongly magnetized and the MHD wavespeeds get close to the speed of light. Computational efforts have focused on simulating kinematically relativistic turbulence to explore appropriate generalizations of the Kolomogorov energy specrum. Simulations have also explored MHD dynamos in relativistic settings but found no significant modifications to the non-relativistic case. Turbulence in force-free electrodynamics has now been explored in depth, and the results have been useful for interpreting the damping of magnetospheric oscillations following giant magnetar flares. Insights to the acceleration of non-thermal particles have come from the exploration of ab-initio particle-in-cell simulations of magnetically dominated turbulent plasma. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700