arXiv subjects

Tomek Plewa

Publications and source records attributed to Tomek Plewa.

5 recordsLinked to original sources

arXiv2004

Validating the FLASH Code: Vortex-Dominated Flows

As a component of the Flash Center's validation program, we compare FLASH simulation results with experimental results from Los Alamos National Laboratory. The flow of interest involves the lateral interaction between a planar Ma=1.2 shock wave with a cylinder of gaseous sulfur hexafluoride (SF_6) in air, and in particular the development of primary and secondary instabilities after the passage of the shock. While the overall evolution of the flow is comparable in the simulations and experiments, small-scale features are difficult to match. We focus on the sensitivity of numerical results to simulation parameters.

astro-ph↗

arXiv2004

Simulation of Vortex--Dominated Flows Using the FLASH Code

We compare the results of two--dimensional simulations to experimental data obtained at Los Alamos National Laboratory in order to validate the FLASH code. FLASH is a multi--physics, block--structured adaptive mesh refinement code for studying compressible, reactive flows in various astrophysical environments. The experiment involves the lateral interaction between a planar Ma=1.2 shock wave with a cylinder of gaseous sulfur hexafluoride (SF$_6$) in air. The development of primary and secondary flow instabilities after the passage of the shock, as observed in the experiments and numerical simulations, are reviewed and compared. The sensitivity of numerical results to several simulation parameters are examined. Computed and experimentally measured velocity fields are compared. Motivation for experimental data in planes parallel to the cylinder axis is provided by a speculative three--dimensional simulation.

astro-ph↗

arXiv2002

Sgr A* and Sgr A East: Intimate Life in the Galactic Center

A hydrodynamic interaction between an old supernova remnant and a massive black hole is studied with the help of a high-resolution adaptive mesh refinement code. A series of multidimensional numerical models is obtained for a fixed distance between supernova explosion site and the black hole but different densities of the ambient medium. The interaction between the shell of the supernova remnant and the black hole results in a rapid increase of the emission from the vicinity of the black hole. Light curves of the gas heated by gravitational compression and hydrodynamical interactions are obtained assuming optically thin conditions. It is shown that the duration of the event and the peak luminosity critically depend on the density of the ambient medium. The model is applied to the data obtained by the Chandra satellite for the Galactic center.

astro-ph↗

arXiv2000

AMRA: An Adaptive Mesh Refinement Hydrodynamic Code for Astrophysics

Implementation details and test cases of a newly developed hydrodynamic code, AMRA, are presented. The numerical scheme exploits the adaptive mesh refinement technique coupled to modern high-resolution schemes which are suitable for relativistic and non-relativistic flows. Various physical processes are incorporated using the operator splitting approach, and include self-gravity, nuclear burning, physical viscosity, implicit and explicit schemes for conductive transport, simplified photoionization, and radiative losses from an optically thin plasma. Several aspects related to the accuracy and stability of the scheme are discussed in the context of hydrodynamic and astrophysical flows.

astro-ph↗

arXiv2000

Numerical hydrodynamics: SPH vs. AMR

The advantages and disadvantages of two approaches to astrophysical hydrodynamics, Smoothed Particle Hydrodynamics and Adaptive Mesh Refinement, are briefly discussed together with some current problems of computational hydrodynamics.

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