A Class of Physically Motivated Closures for Radiation Hydrodynamics - Astrophysics > Instrumentation and Methods for AstrophysicsReport as inadecuate




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Abstract: Radiative transfer and radiation hydrodynamics use the relativistic Boltzmannequation to describe the kinetics of photons. It is difficult to solve thesix-dimensional time-dependent transfer equation unless the problem is highlysymmetric or in equilibrium. When the radiation field is smooth, it is naturalto take angular moments of the transfer equation to reduce the degrees offreedom. However, low order moment equations contain terms that depend onhigher order moments. To close the system of moment equations, approximationsare made to truncate this hierarchy. Popular closures used in astrophysicsinclude flux limited diffusion and the M1 closure, which are rather ad hoc anddo not necessarily capture the correct physics. In this paper, we propose a newclass of closures for radiative transfer and radiation hydrodynamics. We startfrom a different perspective and highlight the consistency of a fullyrelativistic formalism. We present a generic framework to approximate radiativetransfer based on relativistic Grad-s moment method. We then derive a 14-fieldmethod that minimizes unphysical photon self-interaction.



Author: Chi-kwan Chan CfA

Source: https://arxiv.org/



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