A coupled FEM/BEM formulation and parallel implementation for acoustic radiation in moving flows

In this dissertation, an advanced coupled finite element/boundary element formulation with hypersingular integral equation for acoustic radiation in a subsonic non-uniform potential flow is developed. 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 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. A hypersingular integral equation for acoustic radiation in a subsonic uniform flow is presented to overcome the nonuniqueness difficulty in the boundary integral formulation with the Burton and Miller method (1971). Although the nonuniqueness difficulty in the conventional Helmholtz integral formulation has been well studied before, it is shown in this dissertation that this difficulty becomes more severe in the presence of a mean flow. A generalized normal-derivative operator is defined to derive the hypersingular integral equation from the original boundary integral equation. Regularization of the hypersingular kernels is performed to render the integral equation numerically integrable. Theoretical derivation is first given for a general three-dimensional formulation. The resulting hypersingular integral equation is then reduced to the axisymmetric case for numerical implementation. The parallelization of the formulation is explored, and the parallel algorithm is implemented with the PVM (Parallel Virtual Machine) and a dynamically-distributed parallel computation scheme (DDPCS) on heterogeneous virtual computer system. Numerical experiments verify the formulation and the parallel implementation.