Combined finite element-boundary element analysis of a viscoelastic anechoic panel for underwater applications

In this paper the combined finite element-boundary element method is applied to the analysis of the sound-structure interaction around a multi-layered anechoic baffle. The baffle is made of three layers: an aluminium backing supports a second layer of highly butyl rubber. The third layer, loaded polyurethane, presents a regular grid of steep shaped cones with a fluid-matching function. The viscoelastic materials are fully modelled into the finite element method using linear integral constitutive relationships. The combined FE-BE algorithm is based on a partial application of the Burton and Miller Helmholtz gradient formulation to overcome non-uniqueness problems. Examples of analysis of acoustic scattering in a range of frequencies typical of underwater communications are given together with a practical application of the structure