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Recently Atalla et al. [J. Acoust. Soc. Am. 104, 1444–1452 (1998)] and Debergue et al. [J. Acoust. Soc. Am. 106, 2383–2390 (1999)] presented a weak integral formulation and the general boundary conditions for a mixed pressure-displacement version of the Biot’s poroelasticity equations. Finite element discretization was applied to the formulation to solve 3D vibro-acoustic problems involving elastic, acoustic, and poroelastic domains. In this letter, an enhancement of the weak integral formulation is proposed to facilitate its finite element implementation. It is shown that this formulation simplifies the assembly process of the poroelastic medium, the imposition of its boundary conditions, and its coupling with elastic and acoustic media.

A variational principle in terms of displacements in the fluid and the structure with a penalty for irrotationatity of displacement in the fluid is developed for the analysis of harmonic vibrations of ideal compressible fluid and elastic structure systems. Its discretization by the finite element method leads to an algebraic eigenvalue problem with a positive definite symmetric banded matrix. Numerical examples obtained for pure acoustic cases and coupled cases show the efficiency of the method.

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The development of materials both rigid and light with high damping effect and acoustic insulation is possible by using a multilayer panel with viscoelastic material. The rigidity of a multilayer panel is provided by its elastic layers, and damping is provided by viscoelastic layers. Prediction of the behavior of such systems in the conception phase is very important to determine the most important parameters in a multilayer panel in the aim to maximize insulation and to properly design this panel for several applications. In this work we have developed a model based on transfer matrix method, which is an analytic method to predict behavior of infinite layer subjected to a plane wave with an oblique incidence.

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SUMMARYIn order to study problems on fluid-structure interaction, we have used a mixed formulation which couples the classical functional of the structure with a new variational formulation by integral equations for the fluid. This formulation has the advantage over the finite element methods of avoiding the discretization of the fluid domain. Furthermore, unlike collocation methods, the explicit calculation of the Hadamard finite part of the singular integra!s is avoided. This leads after discretization by boundary finite elements to a small and symmetrical algebraic system.Typical examples are presented that demonstrate the efficiency of this variational formulation by studying the sound transmission through a baffled plane structure and through a flexible panel backed by a rigid cavity. These include the calculation of the transmission loss factor and the determination of which modes dominate the noise transmission. Good agreement is obtained between numerical results and analytical results found in the literature.