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Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
On Validating an Astrophysical Simulation Code
In this paper, we focus 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 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 multilayer 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 multilayer target experiments showed good agreement with the experimental results, but our simulations of the Rayleigh-Taylor instability did not agree well with the experimental results. We discuss our findings and present results of additional simulations undertaken to further investigate the Rayleigh-Taylor instability.

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Experimental X-ray radiographs
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Simulation setup
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Simulated X-Ray radiographs


Validating Astrophysical Simulation Codes
Astrophysical simulations model phenomena that can't be fully reproduced terrestrially. Validation then requires carefully devising feasible experiments with the relevant physics. In this paper we describe validating simulations against experiments that probe fluid instabilities, nuclear burning, and radiation transport, and then discuss insights from – and the limitations of – these tests.

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Multimode Rayleigh-Taylor results
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Multimode Rayleigh-Taylor mixing
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Irradiation in a pipe