A family of second-order boundary dampers for finite element analysis of two and three-dimensional problems in transient exterior acoustics

Numerical modelling of exterior acoustics problems involving infinite mediu m requires truncation of the medium at a finite distance from the obstacle or the structure and use of non-reflecting boundary condition at this trunc ation surface to simulate the asymptotic behaviour of radiated waves at far field. In the context of the finite element method, Bayliss-Gunzburger-Tur kel (BGT) boundary conditions are well suited since they are local in both space and time. These conditions involve 'damper' operators of various orde rs, which work on acoustic pressure p and they have been used in time harmo nic problems widely and in transient problems in a limited way. Alternative forms of second-order BGT operators, which work on (p) over dot (time deri vative of p) had been suggested in an earlier paper for 3D problems but the y were neither implemented nor validated. This paper presents detailed form ulations of these second-order dampers both for 2D and 3D problems, impleme nts them in a finite element code and validates them using appropriate exam ple problems. The developed code is capable of handling exterior acoustics problems involving both Dirichlet and Neumann boundary conditions. Copyrigh t (C) 2000 John Wiley & Sons, Ltd.