Wave propagation and scattering in computational aeroacoustics

This paper describes predictions of model problems in computational aeroacoustics. Two problem classes are considered: The first (Workshop Category 3, Problem 1 and 2) considers two-dimensional wave propagation and non-reflecting boundary conditions in the presence of a mean flow. The second (Workshop Category 4, Problem 1) examines wall boundary conditions. For the last problem we introduce the Impedance Mismatch Method (IMM) to treat the solid wall boundaries. In this method the solid wall is simulated using a wall region in which the characteristic impedance is set to a different value to that in the fluid region. This method has advantages over traditional solid wall boundary conditions including simplicity of coding, speed of computations, and the ability to treat curved boundaries efficiently. Several numerical examples are given in addition to the Workshop Problems. The discretization of the Euler equations is performed in all cases with a Dispersion-Relation-Preserving (DRP) algorithm. The numerical results are compared with either analytical solutions or solutions obtained using traditional solid wall boundary conditions.