Calibrating an updated SPH scheme within GCD+

TL;DR

This paper adapts a modern smoothed particle hydrodynamics scheme with improved artificial viscosity and thermal conductivity to the GCD+ code, enhancing its ability to model fluid instabilities and discontinuities accurately.

Contribution

It introduces an updated SPH scheme with specific implementations of viscosity and thermal conductivity, optimized smoothing lengths, and demonstrates improved modeling of fluid instabilities in galactic simulations.

Findings

GCD+ can now model Kelvin-Helmholtz instabilities as well as mesh codes like Athena.

Optimal smoothing length corresponds to about 58 neighbor particles for best results.

The new scheme outperforms previous versions in hydrodynamics tests.

Abstract

We adapt a modern scheme of smoothed particle hydrodynamics (SPH) to our tree N-body/SPH galactic chemodynamics code GCD+. The applied scheme includes imple- mentations of the artificial viscosity switch and artificial thermal conductivity pro- posed by Morris & Monaghan (1997), Rosswog & Price (2007) and Price (2008), to model discontinuities and Kelvin-Helmholtz instabilities more accurately. We first present hydrodynamics test simulations and contrast the results to runs undertaken without artificial viscosity switch or thermal conduction. In addition, we also explore the different levels of smoothing by adopting larger or smaller smoothing lengths, i.e. a larger or smaller number of neighbour particles, Nnb. We demonstrate that the new version of GCD+ is capable of modelling Kelvin-Helmholtz instabilities to a simi- lar level as the mesh code, Athena. From the Gresho vortex, point-like explosion and self-similar collapse tests, we conclude that setting the smoothing length to keep the number of neighbour particles as high as Nnb~58 is preferable to adopting smaller smoothing lengths. We present our optimised parameter sets from the hydrodynamics tests.