  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 described a
method in which local fluid 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 1024^3 grid to study
the kinetic SZ effect. The KSZ power spectrum is broadly peaked at l~10^4 with
temperature fluctuations on micro Kelvin levels.
