Acoustic modeling of light and non-cohesive poro-granular materials with a fluid/fluid model

摘要

Poro-granular materials are studied, and a model adapted to characterize their acoustic behaviour is presented. Biot's theory is used to obtain this model but a great simplification is brought to classical formulation. Indeed, a solid phase being made of a non-cohesive poro-granular material, a specific continuum constitutive model is used to characterize its behaviour. The macroscopic coefficient of friction that takes into account friction and collision phenomena is then neglected under specific conditions. This strong assumption does not apply for all kinds of granular materials and for any solicitations: its validity is discussed for particular materials. The solid/fluid model of Biot's theory is then transformed to an equivalent fluid/fluid model. The complexity of the classical formulation is significantly reduced since only two degrees of freedom are used: the solid and fluid pressures. A 1D case is then treated to present the simplicity of the formulation, and applied to a poro-granular material made of expanded polystyrene beads. Intrinsic parameters of this material are adjusted thanks to surface impedances measured with a stationary waves tube. Finally, a study on thermal and viscous dissipations is realized and associated with a study on pressure and velocity distribution in the sample.