NONREFLECTING FINITE-ELEMENT SCHEMES FOR 3-DIMENSIONAL ACOUSTIC-WAVES

The finite element solution of problems involving three-dimensional ac oustic waves in an infinite wave guide, and in the infinite medium aro und a structure is considered. Such problems are typical in structural acoustics, and this paper concentrates on the efficient numerical tre atment of the infinite acoustic medium away from the structure. The un bounded domain is truncated by means of an artificial boundary B. On B , non-reflecting boundary conditions are used; these are either nonloc al Dirichlet-to-Neumann conditions, or their localized counterparts. F or the high-order localized conditions, special three-dimensional fini te elements are constructed for use in the layer adjacent to B. The pe rformance of the nonlocal and localized boundary conditions is compare d via numerical experiments involving a three-dimensional wave guide.