Numerical Modelling of Dynamics of Light Porous Materials

Abstract: Porous materials are among the most commonly used materials for noise and vibration reduction in modern transportation vehicles. To design, industrially relevant, weight and cost effective noise and vibration measures, there is a need for general prediction models capable of representing the elasto-acoustic behaviour of such materials. The objective of the present work, is to contribute to the modelling of the inherent fluid-structure interaction phenomena related to porous materials. The modelling approach chosen allows for solution of problems having multiple layers of materials with complicated geometrical shapes and including effects of different boundary conditions along the interfaces to other fluid and solid materials. To solve general three dimensional dynamic problems involving porous materials, a finite element formulation of Biot's equations, describing the fluid-structure interaction in porous materials is proposed. The resulting discrete equation systems, including coupling matrices to other fluid and solid materials, have symmetric matrices and are thus readily implemented into standard finite element software packages. Effects of viscous dissipation, thermal interaction, solid frame disspation and inertial coupling are taken into account. In addition, a finite element formulation of a simplified equivalent fluid model for low stiffness porous materials is proposed.