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Soutenance pour obtenir l’Habilitation à Diriger des Recherches présentée par Olivier DAZEL

Soutenance pour obtenir l’Habilitation à Diriger des Recherches présentée par Olivier DAZEL

le mardi 31 août 2011 à 14h30 en salle de visioconférence à l’ETNA

sujet : Numerical methods for the Biot theory in acoustics

devant le jury composé de :
Noureddine Atalla, Professeur, GAUS (Canada) - rapporteur
Jean-François Deü, Professeur, LMSSC-CNAM (Paris) - rapporteur
Peter Göransson, Professeur, MWL (Suède) - rapporteur
Jean-Pierre Coyette, Professeur, UCLouvain (Belgique)
Claude Depollier, Professeur, LAUM (Le Mans)
Marie-Annick Galland, Professeur, LMFA-ECL (Lyon)
Claude-Henri Lamarque, Dr-HDR, DGCB-ENTPE (Lyon)
Franck Sgard, Dr-HDR, IRSST (Canada)

Résumé :
Sound absorbing materials (porous media) are attractive because of their property of mechanical energy dissipation. They are key structures for the acoustic community in order to find answers to the social demand of minimizing noise annoyances. This work is concerned by the numerical modelling of the dynamical behavior of these materials. Three main aspects are considered : physical models, analytical and numerical methods.

An original formulation of the Biot theory has been proposed. This representation simplifies the Biot formalism thereby leading to shorter analytical expressions without making physical assumptions. It has then allowed to extend the Biot formalism to several types of sound absorbing materials (eg. Transverse isotropic ...). In addition, an original nonlinear Biot theory has been proposed and applied to granular materials. Double porosity materials with a deformable frame are also considered. All these models have been compared to experiments.

Models have also been developed for porous structures with irregularities. It can be irregular interfaces, solid and fluid inclusions or a grating in the rigid backing. One main objective is to improve the absorption of the porous structure and mainly to optimize them in the low frequency range. Component Mode Synthesis techniques for poroelastic structures are then presented. The main idea of these techniques consists in using simple modal forms of conservative and decoupled problems and to complete them in an efficient manner so as to neglect only a minimum of information in the modal truncation. The concept of attachment modes introduced by Craig & Chang was used so as to take into account the response of non-preserved modes in the truncation but also to consider intercoupling between solid and fluid modes.