Application of the coupled FEM/BEM technique to structural acoustic using consistent isoparametric elements

In this paper, the coupled FEM/BEM technique is used for the solution of problems in structural acoustics. Problems in this category include: the radiation and scattering of sound from elastic thin shells submerged in a heavy fluid such as sea water, and the sound filed generated within a vehicle passenger compartment of aircraft cabin due to vibration of the surrounding structure. The finite element method (FEM) is applied to the structure and the boundary element method (BEM) is applied to the fluid. Such a coupling strategy takes advantage of the features of versatile and well-developed structural FEM codes and the distinct features of the BEM for acoustic problems. Quadratic isoparametric elements are used in both the FEM and BEM models. Continuity conditions of pressure and displacements are enforced at the fluid-structure interface, including those points where the normal vector is not uniquely defined. The size of the problem can be considerably reduced by using the Guyan reduction technique. Several exterior and interior example problems are solved to test the accuracy of the numerical solution.