Solution of the FE-BE Coupled Eigenvalue Problem for Immersed Ship-like Structures

Abstract

-1-To predict the vibro-acoustic behavior of structures, both a structural problem and an acoustic problem have to be solved. For thin structures immersed in water a strong interaction between the structural domain and fluid domain occurs. This significantly alters the resonance frequencies. In this paper, the structure is modeled by the finite element method. The exterior acoustic problem is solved by a fast boundary element method employing hierarchical matrices. A FE-BE formulation is presented, which allows the solution of the coupled eigenvalue problem and thus the prediction of the coupled eigenfrequencies and mode shapes. It is based on a Schur complement formulation of the FE-BE system yielding a generalized eigenvalue problem. A Krylov-Schur solver is applied for its efficient solution. Hereby, the compressibility of the fluid is neglected. The applicability of the proposed formulation is demonstrated on a ship-like cylindrical test structure.