Nonlinear Investigation Of Oscillations In Radiating Shockwaves
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Date
2020-09-24
Authors
Keever, Erik
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
Strong shockwaves are a common phenomenon throughout the universe. Linear analysis indicates that when the postshock gas cools with a volume emission rate $\Lambda \propto \rho^2 T^\theta$ that for many physically realizable values of $\theta$ the cooling region should be subject to both one-dimensional (`radial' in the accretion context) and transverse instabilities. The hydrodynamic and numeric theory underlying the GPU-Imogen parallel GPU-accelerated fluid dynamic code is presented. This accelerated code was used to simulate over one thousand combinations of Mach, adiabatic index and radiation law $\theta$ to their final nonlinear state in one dimension, which gives a comprehensive dictionary of the expected observable output as a function of the input parameters. The same code was used to examine the fully nonlinear development of transverse instabilities in two dimensions. It is found that the same radial modes expected to dominate most of parameter space, the F and first overtone, suffer their cold zones degenerating into turbulence which shuts down the characteristic large, periodic luminosity fluctuations expected from the one dimensional case.
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Keywords
gpu, radiation, shocks