Application of the finite element method to acoustic scattering problems

For aircraft, scattering of engine and rotor noise from the fuselage and wings can considerably influence community and interior noise levels. Here the finite element method (FEM) is considered as a modeling technique because of its ability to solve for a broad range of governing equations and its potential efficiency advantages over the more commonly used boundary element method. With FEM, however, the data storage requirements become very demanding for three-dimensional problems involving realistic geometries and frequency ranges. To enable large FEM problems to be tackled using relatively modest computing facilities, the computational cost is addressed at several levels. The extent of the mesh is reduced using infinite elements; the data are manipulated using a sparse storage scheme; and an iterative complex solver in combination with a preconditioner is implemented. Validation of the code is illustrated by comparison with classical analytical solutions for plane wave scattering from a sphere. To demonstrate the potential of the technique, results are calculated for three-dimensional acoustic scattering off a fuselage geometry at useful frequencies.