Fornax: a Flexible Code for Multiphysics Astrophysical Simulations

TL;DR

Fornax is a versatile, high-fidelity radiation hydrodynamics code designed for astrophysical simulations, validated through extensive tests and capable of scaling efficiently on large computational resources.

Contribution

This work introduces Fornax, a new multi-group, multi-dimensional RHD code with advanced algorithms and extensive validation across diverse physical regimes.

Findings

Fornax accurately captures complex radiation hydrodynamics effects.

The code demonstrates excellent numerical fidelity in various tests.

Fornax scales efficiently on over 100,000 MPI tasks.

Abstract

This paper describes the design and implementation of our new multi-group, multi-dimensional radiation hydrodynamics (RHD) code Fornax and provides a suite of code tests to validate its application in a wide range of physical regimes. Instead of focusing exclusively on tests of neutrino radiation hydrodynamics relevant to the core-collapse supernova problem for which Fornax is primarily intended, we present here classical and rigorous demonstrations of code performance relevant to a broad range of multi-dimensional hydrodynamic and multi-group radiation hydrodynamic problems. Our code solves the comoving-frame radiation moment equations using the M1 closure, utilizes conservative high-order reconstruction, employs semi-explicit matter and radiation transport via a high-order time stepping scheme, and is suitable for application to a wide range of astrophysical problems. To this end, we first describe the philosophy, algorithms, and methodologies of Fornax and then perform numerous stringent code tests, that collectively and vigorously exercise the code, demonstrate the excellent numerical fidelity with which it captures the many physical effects of radiation hydrodynamics, and show excellent strong scaling well above 100k MPI tasks.