MONTE CARLO RADIATIONHYDRODYNAMICS WITH IMPLICIT METHODS
Abstract
We explore the application of Monte Carlo transport methods to solving coupled radiationhydrodynamics (RHD) problems. We use a timedependent, frequencydependent, threedimensional radiation transport code that is special relativistic and includes some detailed microphysical interactions such as resonant line scattering. We couple the transport code to two different onedimensional (nonrelativistic) hydrodynamics solvers: a spherical Lagrangian scheme and a Eulerian Godunov solver. The gas–radiation energy coupling is treated implicitly, allowing us to take hydrodynamical timesteps that are much longer than the radiative cooling time. We validate the code and assess its performance using a suite of radiation hydrodynamical test problems, including ones in the radiation energy dominated regime. We also develop techniques that reduce the noise of the Monte Carlo estimated radiation force by using the spatial divergence of the radiation pressure tensor. The results suggest that Monte Carlo techniques hold promise for simulating the multidimensional RHD of astrophysical systems.
 Authors:
 Physics Department, University of California, Berkeley, CA 94720 (United States)
 Publication Date:
 OSTI Identifier:
 22519943
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Astrophysical Journal, Supplement Series; Journal Volume: 217; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTROPHYSICS; FREQUENCY DEPENDENCE; HYDRODYNAMICS; LAGRANGIAN FUNCTION; MONTE CARLO METHOD; RADIANT HEAT TRANSFER; RADIATION PRESSURE; RADIATION TRANSPORT; RADIATIVE COOLING; RELATIVISTIC RANGE; SCATTERING; TENSORS; TIME DEPENDENCE
Citation Formats
Roth, Nathaniel, and Kasen, Daniel, Email: nathaniel.roth@berkeley.edu. MONTE CARLO RADIATIONHYDRODYNAMICS WITH IMPLICIT METHODS. United States: N. p., 2015.
Web. doi:10.1088/00670049/217/1/9.
Roth, Nathaniel, & Kasen, Daniel, Email: nathaniel.roth@berkeley.edu. MONTE CARLO RADIATIONHYDRODYNAMICS WITH IMPLICIT METHODS. United States. doi:10.1088/00670049/217/1/9.
Roth, Nathaniel, and Kasen, Daniel, Email: nathaniel.roth@berkeley.edu. 2015.
"MONTE CARLO RADIATIONHYDRODYNAMICS WITH IMPLICIT METHODS". United States.
doi:10.1088/00670049/217/1/9.
@article{osti_22519943,
title = {MONTE CARLO RADIATIONHYDRODYNAMICS WITH IMPLICIT METHODS},
author = {Roth, Nathaniel and Kasen, Daniel, Email: nathaniel.roth@berkeley.edu},
abstractNote = {We explore the application of Monte Carlo transport methods to solving coupled radiationhydrodynamics (RHD) problems. We use a timedependent, frequencydependent, threedimensional radiation transport code that is special relativistic and includes some detailed microphysical interactions such as resonant line scattering. We couple the transport code to two different onedimensional (nonrelativistic) hydrodynamics solvers: a spherical Lagrangian scheme and a Eulerian Godunov solver. The gas–radiation energy coupling is treated implicitly, allowing us to take hydrodynamical timesteps that are much longer than the radiative cooling time. We validate the code and assess its performance using a suite of radiation hydrodynamical test problems, including ones in the radiation energy dominated regime. We also develop techniques that reduce the noise of the Monte Carlo estimated radiation force by using the spatial divergence of the radiation pressure tensor. The results suggest that Monte Carlo techniques hold promise for simulating the multidimensional RHD of astrophysical systems.},
doi = {10.1088/00670049/217/1/9},
journal = {Astrophysical Journal, Supplement Series},
number = 1,
volume = 217,
place = {United States},
year = 2015,
month = 3
}

This work describes how to couple a hybrid Implicit Monte Carlo Diffusion (HIMCD) method with a Lagrangian hydrodynamics code to evaluate the coupled radiation hydrodynamics equations. This HIMCD method dynamically applies Implicit Monte Carlo Diffusion (IMD) [1] to regions of a problem that are opaque and diffusive while applying standard Implicit Monte Carlo (IMC) [2] to regions where the diffusion approximation is invalid. We show that this method significantly improves the computational efficiency as compared to a standard IMC/Hydrodynamics solver, when optically thick diffusive material is present, while maintaining accuracy. Two test cases are used to demonstrate the accuracy andmore »

Methods for coupling radiation, ion, and electron energies in grey Implicit Monte Carlo
We present three methods for extending the Implicit Monte Carlo (IMC) method to treat the timeevolution of coupled radiation, electron, and ion energies. The first method splits the ion and electron coupling and conduction from the standard IMC radiationtransport process. The second method recasts the IMC equations such that part of the coupling is treated during the Monte Carlo calculation. The third method treats all of the coupling and conduction in the Monte Carlo simulation. We apply modified equation analysis (MEA) to simplified forms of each method that neglects the errors in the conduction terms. Through MEA we show thatmore » 
Piecewise linear discretization of Symbolic Implicit Monte Carlo radiation transport in the difference formulation
We describe a Monte Carlo solution for time dependent photon transport, in the difference formulation with the material in local thermodynamic equilibrium (LTE), that is piecewise linear in its treatment of the material state variable. Our method employs a Galerkin solution for the material energy equation while using Symbolic Implicit Monte Carlo (SIMC) to solve the transport equation. In constructing the scheme, one has the freedom to choose between expanding the material temperature, or the equivalent black body radiation energy density at the material temperature, in terms of finite element basis functions. The former provides a linear treatment of themore »