Modelling astrophysical fluids with particles

TL;DR

This paper reviews recent advancements in Smoothed Particle Hydrodynamics (SPH) methods for astrophysical fluid modeling, highlighting technical improvements and their application in both Newtonian and relativistic regimes.

Contribution

It introduces new technical developments in SPH, including improved kernels and dissipation control, and demonstrates their implementation in the first general-relativistic SPH code for neutron star simulations.

Findings

Enhanced SPH code MAGMA2 with improved accuracy

First particle-based relativistic fluid code SPHINCS_BSSN

Successful simulation of neutron stars with self-consistent spacetime evolution

Abstract

Computational fluid dynamics is a crucial tool to theoretically explore the cosmos. In the last decade, we have seen a substantial methodological diversification with a number of cross-fertilizations between originally different methods. Here we focus on recent developments related to the Smoothed Particle Hydrodynamics (SPH) method. We briefly summarize recent technical improvements in the SPH-approach itself, including smoothing kernels, gradient calculations and dissipation steering. These elements have been implemented in the Newtonian high-accuracy SPH code MAGMA2 and we demonstrate its performance in a number of challenging benchmark tests. Taking it one step further, we have used these new ingredients also in the first particle-based, general-relativistic fluid dynamics code that solves the full set of Einstein equations, SPHINCS_BSSN. We present the basic ideas and equations and demonstrate the code performance at examples of relativistic neutron stars that are evolved self-consistently together with the spacetime.