On Validating an Astrophysical Simulation Code

We present a case study of validating an astrophysical simulation code. Our study focuses on validating FLASH, a parallel, adaptive-mesh hydrodynamics code for studying the compressible, reactive flows found in many astrophysical environments. We describe the astrophysics problems of interest and the challenges associated with simulating these problems. We describe methodology and discuss solutions to difficulties encountered in verification and validation. We describe verification tests regularly administered to the code, present the results of new verification tests, and outline a method for testing general equations of state. We present the results of two validation tests in which we compared simulations to experimental data. The first is of a laser-driven shock propagating through a multi-layer target, a configuration subject to both Rayleigh-Taylor and Richtmyer-Meshkov instabilities. The second test is a classic Rayleigh-Taylor instability, where a heavy fluid is supported against the force of gravity by a light fluid. Our simulations of the multi-layer target experiments showed good Center for Astrophysical Thermonuclear Flashes, The University of Chicago, Chicago, IL 60637 Department of Astronomy & Astrophysics, The University of Chicago, Chicago, IL 60637 Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637 Nicolaus Copernicus Astronomical Center, Bartycka 18, 00716 Warsaw, Poland Department of Computer Science, The University of Chicago, Chicago, IL 60637 Lawrence Livermore National Laboratory, Livermore, CA 94550 University of Michigan Ann Arbor, MI 48105 Dept of Astronomy and Astrophysics, The University of California, Santa Cruz, Santa Cruz, CA 95064 UMBC/GEST Center, NASA/GSFC, Greenbelt, MD 20771