Hydrodynamical Simulations of the IGM at High Mach Numbers

Abstract

We present a new approach to doing Eulerian computational fluid dynamics that is designed to work at high Mach numbers encountered in hydrodynamical simulations of the IGM. In conventional Eulerian CFD, the thermal energy is poorly tracked in supersonic bulk flows where local fluid variables cannot be accurately separated from the much larger bulk flow components. We describe a method in which local quantities can be directly tracked and the Eulerian fluid equations solved in a local frame moving with the flow. The new algorithm has been used to run large hydrodynamical simulations on a 1024³ grid to study the kinetic SZ effect. The KSZ power spectrum is broadly peaked at l ∼ 10⁴ with temperature fluctuations ∼ 1μK.