CASTRO: A New Compressible Astrophysical Solver. II. Gray Radiation Hydrodynamics

TL;DR

This paper introduces a flux-limited gray radiation solver integrated into the CASTRO astrophysics code, employing adaptive mesh refinement and a split hyperbolic-parabolic approach for efficient radiation hydrodynamics simulations.

Contribution

It presents a novel radiation solver combining explicit hyperbolic and implicit parabolic methods within an adaptive mesh framework for astrophysical applications.

Findings

Successful implementation of the radiation solver in CASTRO

Demonstrated accuracy and stability in test problems

Enhanced capability for astrophysical radiation hydrodynamics simulations

Abstract

We describe the development of a flux-limited gray radiation solver for the compressible astrophysics code, CASTRO. CASTRO uses an Eulerian grid with block-structured adaptive mesh refinement based on a nested hierarchy of logically-rectangular variable-sized grids with simultaneous refinement in both space and time. The gray radiation solver is based on a mixed-frame formulation of radiation hydrodynamics. In our approach, the system is split into two parts, one part that couples the radiation and fluid in a hyperbolic subsystem, and another parabolic part that evolves radiation diffusion and source-sink terms. The hyperbolic subsystem is solved explicitly with a high-order Godunov scheme, whereas the parabolic part is solved implicitly with a first-order backward Euler method.