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SUMMARYTo predict the sound radiation of structures, both a structural problem and an acoustic problem have to be solved. In case of thin structures and dense fluids, a strong coupling scheme between the two problems is essential, since the feedback of the acoustic pressure onto the structure is not negligible. In this paper, the structural part is modeled with the finite element (FE) method. An interface to a commercial FE package is set up to import the structural matrices. The exterior acoustic problem is efficiently modeled with the Galerkin boundary element (BE) method. To overcome the well-known drawback of fully populated system matrices, the fast multipole method is applied. Different coupling formulations are investigated. They are either based on the Burton-Miller approach or use a mortar coupling scheme. For all cases, iterative solvers with different preconditioners are used. The efficiency with respect to their memory consumption and computation time is compared for a simple model problem. At the end of the paper, a more complex structure is simulated.

SUMMARYFluid-structure coupled problems are investigated to predict the vibro-acoustic behavior of submerged bodies. The finite element method is applied for the structural part, whereas the boundary element method is used for the fluid domain. The focus of this paper is on partly immersed bodies. The fluid problem is favorably modeled by a half-space formulation. This way, the Dirichlet boundary condition on the free fluid surface is incorporated by a half-space fundamental solution. A fast multipole implementation is presented for the half-space problem. In case of a high density of the fluid, the forces due to the acoustic pressure, which act on the structure, cannot be neglected. Thus, a strong coupling scheme is applied. An iterative solver is used to handle the coupled system. The efficiency of the proposed approach is discussed using a realistic model problem