Thesis presented by Romain Rumpler

Efficient finite element approach for structural-acoustic applications including
3D modelling of sound absorbing porous materials.

Submitted March the 13th 2012 to the thesis committee:

Noureddine ATALLA Université de Sherbrooke, Canada Reviewer
Wim DESMET Katholieke Universiteit Leuven (KUL), Belgium Reviewer
Henry J. RICE Trinity College Dublin, Ireland Opponent
Laurent CHAMPANEY École Normale Supérieure de Cachan, France President
Antoine LEGAY Cnam Paris, France Co-supervisor
Peter GÖRANSSON Royal Institute of Technology (KTH), Sweden Main supervisor
Jean-François DEÜ Cnam Paris, France Main supervisor


In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under time harmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.

First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.

In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.

A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.

Laboratoire de Mécanique des Structures et des Systèmes Couplés - LMSSC