Density, temperature radial velocity, and surface density for two models with N = 256³ particles for different artificial viscosities. Top: the classical formulation (Monaghan & Gingold 1983) (model “a”). Bottom: the formulation proposed by Monaghan (1997) and used as a default in the Gadget-2 code (model “b”). In each panel, the blue dashed curve corresponds to the analytical Sedov-Taylor solution while the green dashed curve is the average particle value. The particles indicated in red were directly assigned feedback energy. Because of the lower efficiency of the standard Gadget-2 artificial viscosity (bottom), some gas particles can penetrate into the ISM through the supernova shell. This is visible in anisotropies in the density behind the shock front.