Numerical approaches for multidimensional simulations of stellar explosions

TL;DR

This paper presents numerical algorithms for accurately initializing multidimensional stellar explosion simulations from 1D models, ensuring conservation laws and realistic turbulence perturbations, applicable across astrophysics and cosmology.

Contribution

The authors develop conservation-preserving mapping schemes and turbulence initialization methods for multidimensional stellar explosion simulations from 1D models.

Findings

Conservation laws are maintained after mapping 1D profiles onto multidimensional grids.

Velocity perturbations reproduce Kolmogorov turbulence spectra in simulations.

The methods are applicable to a range of astrophysical and cosmological simulations.

Abstract

We introduce numerical algorithms for initializing multidimensional simulations of stellar explosions with 1D stellar evolution models. The initial mapping from 1D profiles onto multidimensional grids can generate severe numerical artifacts, one of the most severe of which is the violation of conservation laws for physical quantities. We introduce a numerical scheme for mapping 1D spherically-symmetric data onto multidimensional meshes so that these physical quantities are conserved. We verify our scheme by porting a realistic 1D Lagrangian stellar profile to the new multidimensional Eulerian hydro code CASTRO. Our results show that all important features in the profiles are reproduced on the new grid and that conservation laws are enforced at all resolutions after mapping. We also introduce a numerical scheme for initializing multidimensional supernova simulations with realistic perturbations predicted by 1D stellar evolution models. Instead of seeding 3D stellar profiles with random perturbations, we imprint them with velocity perturbations that reproduce the Kolmogorov energy spectrum expected for highly turbulent convective regions in stars. Our models return Kolmogorov energy spectra and vortex structures like those in turbulent flows before the modes become nonlinear. Finally, we describe approaches to determining the resolution for simulations required to capture fluid instabilities and nuclear burning. Our algorithms are applicable to multidimensional simulations besides stellar explosions that range from astrophysics to cosmology.