The vibrational analysis of ships involves the solution of a coupled fluid-structure interaction problem in order to simulate the inertia response of the water to the structural vibrations. The paper describes a coupled FE-BE procedure for the computational solution of this problem. Regarding the structural equations, special emphasis is put on the modeling of damping. Various models of damping, in particular local damping, are discussed and implemented into the FE-model of the ship structure. The computational results are compared to data from large-scale measurements.

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Simulation of vibroacoustic behavior of submerged bodies necessitates dealing with fluid-structure coupled problems. In case of a high density of the fluid, the feedback of the acoustic pressure onto the structure cannot be neglected and a fully coupled system must be investigated. In this work, the finite element method (FEM) is used for the structural part. The commercial finite element package ANSYS is applied for setting up the mass and stiffness matrices. The boundary element method (BEM) is well suited for simulating the sound propagation in the unbounded exterior acoustic fluid domain. Here, the fast multipole method (FMM) is applied to overcome the known bottleneck of classical BE-methods. In the case of partly immersed bodies, Dirichlet boundary conditions on the fluid surface additionally have to be incorporated. This is done by applying a halfspace formulation. The extension of the FMM to this scenario is discussed. Iterative preconditioned solvers are employed and the numerical efficiency is discussed. The applicability of the coupling scheme is demonstrated using a realistic model problem.

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