SACRA-2D: New axisymmetric general relativistic hydrodynamics code with fixed mesh refinement

TL;DR

SACRA-2D is a new axisymmetric general relativistic hydrodynamics code that uses advanced numerical schemes and fixed mesh refinement, demonstrating high accuracy and robustness in simulating complex astrophysical phenomena.

Contribution

The paper introduces SACRA-2D, a novel parallelized GRHD code with improved accuracy using the HLLC Riemann solver and fixed mesh refinement in axisymmetric spacetime.

Findings

Accurate simulations of black hole collisions and neutron star dynamics.

Excellent agreement with existing codes in benchmark tests.

Robust performance in diverse astrophysical scenarios.

Abstract

We present \texttt{SACRA-2D}, a new MPI and OpenMP parallelized, fully relativistic hydrodynamics (GRHD) code in dynamical spacetime under axial symmetry with the cartoon method using the finite-volume shock-capturing schemes for hydrodynamics. Specifically, we implemented the state-of-the-art HLLC Riemann solver and found better accuracy than the standard Total Variation Diminishing Lax-Friedrich Riemann solver. The spacetime evolves under the Baumgarte-Shapiro-Shibata-Nakamura formalism with Z4c constraint propagation. We demonstrate the accuracy of the code with some benchmark tests and excellent agreement with other codes in the literature. A wide variety of test simulations, including the head-on collision of black holes, the migration and collapse of neutron stars, and the collapse of a rotating supermassive star to a massive black hole and a disk, is also performed to show the robustness of our new code.