  The physical processes involved in the advective-acoustic instability are
investigated with 2D numerical simulations. Simple toy models, developped in a
companion paper, are used to describe the coupling between acoustic and
entropy/vorticity waves, produced either by a stationary shock or by the
deceleration of the flow. Using two Eulerian codes based on different second
order upwind schemes, we confirm the results of the perturbative analysis. The
numerical convergence with respect to the computation mesh size is studied with
1D simulations. We demonstrate that the numerical accuracy of the quantities
which depend on the physics of the shock is limited to a linear convergence. We
argue that this property is likely to be true for most current numerical
schemes dealing with SASI in the core-collapse problem, and could be solved by
the use of advanced techniques for the numerical treatment of the shock. We
propose a strategy to choose the mesh size for an accurate treatment of the
advective-acoustic coupling in future numerical simulations.
