A Co-Scaling Grid for Athena++

TL;DR

This paper introduces a co-scaling grid formalism for Athena++ that leverages flow symmetries to improve simulation accuracy and efficiency in astrophysical magnetohydrodynamics problems involving expansion and contraction.

Contribution

It presents a novel co-scaling grid formalism and implementation in Athena++, enabling independent grid evolution based on flow symmetries.

Findings

Improved accuracy in hydrodynamic test cases.

Higher computational efficiency.

Effective handling of expansion and contraction in simulations.

Abstract

We present a co-scaling grid formalism and its implementation in the magnetohydrodynamics code Athena++. The formalism relies on flow symmetries in astrophysical problems involving expansion, contraction, and center-of-mass motion. The grid is evolved at the same time order as the fluid variables. The user specifies grid evolution laws, which can be independent of the fluid motion. Applying our implementation to standard hydrodynamic test cases leads to improved results and higher efficiency, compared to the fixed-grid solutions.