Numerical boundary conditions for sound scattering simulation

A hierarchy of boundary algorithms based both on a decomposition of the flow field and on a characteristic formulation of the conservation equations is introduced for the computation of sound wave scattering by vortical flows. The robustness of the proposed algorithms is analysed. Sound and vorticity wave reflexion at an open boundary are estimated for various mean flows and different sound wave fields. A direct assessment of this algorithm coupled with an interior 2–4 Mac Cormack scheme for sound scattering computations based on the 2D inviscid gas dynamics equations is performed using comparison with theoretical scattering results.