Updated modeling of gas physics in
. Central density slices of the time evolution of a high density cloud in pressure equilibrium in a wind. Time is in units of the Kelvin-Helmholtz growth time. ChaNGa (top) vs GADGET-2 (Springel 2005) (bottom). The color density map shows how with the new SPH formulation of pressure gradients, artificial surface tension is suppressed and instabilities rapidly mix the ‘blob’ with the surrounding medium, while poor handling of contact discontinuities preserve the blob in the now obsolete SPH implementation of GADGET-2. We have verified that ChaNGa gives results quite similar to alternative hydro codes, as the adaptive mesh refinement code ENZO (Collins et al. 2010). This figure was produced with Pynbody (Pontzen et al. 2013).