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Keywords: elastoacoustic, absorbing material, porous medium, acoustic impedance, finite element.

Summary

During the last decades, many studies have focused on passive damping techniques for noise and vibration reduction. Within this context, we propose to investigate and compare finite element modeling of soundproofing material in structural-acoustic internal problems. Two approaches are analyzed: (i) a local wall impedance model and (ii) a more refined approach based on poroelasticity theory.

The coupled system consists of an elastic structure coupled with an internal inviscid, homogeneous and compressible fluid, gravity effect being neglected. Dissipative behavior is introduced through a fluid-structure wall damping at the interface between the two domains.

When acoustic wall impedance is used for modeling the absorbing interface, the problem becomes strongly frequency dependent. In this work, a simplified but rather general constitutive model of Kelvin-Voigt type is used, through the introduction of a scalar interface variable (fluid normal displacement at the interface) which allows the problem to be reduced to a classical vibration damping problem. This impedance model, though local, may represent relatively satisfactory soundproofing materials.

A comparison is carried out with a more refined approach. It consists in a three-dimensional description of the absorbing material at the fluid-structure interface through a Biot-Allard porous type approach. The finite element poroelastic model is written in terms of the solid phase displacement and the interstitial fluid pressure of the porous material. In this case, the dissipative effects of the damping material are expressed by complex quantities which depend on the circular frequency.

The acoustic impedance parameters can be determined starting from intrinsic characteristics of the porous medium by a numerical approach or by an analytical solution. The latter can be obtained for example by considering a laterally infinite poroelastic materials excited by normal incidence plane wave.

Some three-dimensional numerical examples are then presented in order to illustrate and compare these formulations.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 88 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping and M. Papadrakakis Paper 89 Comparison Between Local Wall Impedance and More Refined Poroelastic Models in Vibroacoustics W. Larbi, J.F. Deü and R. Ohayon Structural Mechanics and Coupled Systems Laboratory, Conservatoire National des Arts et Métiers, Paris, France doi:10.4203/ccp.88.89 purchase the full-text of this paper Full Bibliographic Reference for this paper , "Comparison Between Local Wall Impedance and More Refined Poroelastic Models in Vibroacoustics", in B.H.V. Topping, M. Papadrakakis, (Editors), "Proceedings of the Ninth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 89, 2008. doi:10.4203/ccp.88.89 Keywords: elastoacoustic, absorbing material, porous medium, acoustic impedance, finite element. Summary During the last decades, many studies have focused on passive damping techniques for noise and vibration reduction. Within this context, we propose to investigate and compare finite element modeling of soundproofing material in structural-acoustic internal problems. Two approaches are analyzed: (i) a local wall impedance model and (ii) a more refined approach based on poroelasticity theory. The coupled system consists of an elastic structure coupled with an internal inviscid, homogeneous and compressible fluid, gravity effect being neglected. Dissipative behavior is introduced through a fluid-structure wall damping at the interface between the two domains. When acoustic wall impedance is used for modeling the absorbing interface, the problem becomes strongly frequency dependent. In this work, a simplified but rather general constitutive model of Kelvin-Voigt type is used, through the introduction of a scalar interface variable (fluid normal displacement at the interface) which allows the problem to be reduced to a classical vibration damping problem. This impedance model, though local, may represent relatively satisfactory soundproofing materials. A comparison is carried out with a more refined approach. It consists in a three-dimensional description of the absorbing material at the fluid-structure interface through a Biot-Allard porous type approach. The finite element poroelastic model is written in terms of the solid phase displacement and the interstitial fluid pressure of the porous material. In this case, the dissipative effects of the damping material are expressed by complex quantities which depend on the circular frequency. The acoustic impedance parameters can be determined starting from intrinsic characteristics of the porous medium by a numerical approach or by an analytical solution. The latter can be obtained for example by considering a laterally infinite poroelastic materials excited by normal incidence plane wave. Some three-dimensional numerical examples are then presented in order to illustrate and compare these formulations. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £145 +P&P)
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