A coupled FEM/BEM formulation for acoustic radiation in a subsonic non-uniform flow

In this paper, a coupled finite element/boundary element formulation for acoustic radiation from bodies submerged in a subsonic non-uniform flow field is presented. For simplicity, attention is focused on fully axisymmetric problems only. The finite element method (FEM) is applied to the non-uniform flow region, and the boundary element method (BEM) is applied to the uniform flow region. The BEM is based on a direct boundary integral formulation recently developed by Wu and Lee [7] for acoustics in a uniform flow. The major advantage of the direct boundary integral formulation is that the variables in the BEM can be expressed explicitly in terms of the velocity potential and its normal derivative. The coupling between the FEM and the BEM is achieved by converting the BEM model into a radiation admittance matrix to be used as the exterior boundary condition in the FEM model. Numerical examples are given to verify the formulation.