A substructuring FE model for reduction of stuctural acoustic problems
with dissipative interfaces

LMSSC, Cnam, Paris, France

In this work, a fixed-interface component mode synthesis is applied to the acoustic part of a vibroacoustic problem including porous material at interface. The aim is to downsize the problem to the dimension of the interfaces. It leads to a reduced overall number of dofs, by a transformation combining selected normal modes of the components restrained at interface, with the so-called "static modes" obtained by introducing a mobility at the interface dofs. A displacement-pressure (for the structure and the acoustic fluid respectively) formulation is used to describe the vibroacoustic problem, involving a large and non-symmetric coupled problem. For the porous medium at interface, a poroelastic model based on the Biot-Allard theory is used, where fluid and solid phase displacements are retained as primary variables. Acoustic and poroelastic hexahedric elements, structural elastic quad shell element, as well as the proposed reduction method are implemented in the Fortran-based finite element program FEAP. The method is tested on academic examples, and on the concrete car model. A comparison in terms of computational time and accuracy of the results is then conducted, validating the proposed CMS method. Further reduction methods applied to the poroelastic medium itself are under investigation.

Laboratoire de Mécanique des Structures et des Systèmes Couplés - LMSSC