FINITE ELEMENT MODELS FOR ACOUSTIC PROPAGATION ON MEAN FLOWS

This article deals with finite element modelling of acoustic propagation on irrotational subsonic mean flows. The article is in two parts. First, a dispersion analysis is presented for traditional finite element models for the convected Helmholtz problem. The dispersion and stability properties of such formulations are shown to dier in several important respects from those for the standard Helmholtz problem. In the second part of the article a novel formulation is presented which is based on the use of local plane wave solutions to enrich the finite element trial space. The formulation falls within the general framework of a 'Partition of Unity' approach. The presence of mean flow gives local solutions that are anisotropic and inhomogeneous. The eectiveness of the method