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Propagation acoustique dans les guides d'ondes courbes et Problème avec source dans un écoulement cisaillé

Abstract : Two studies are presented in this work, both concerned with modal propagation in waveguides : the acoustic propagation in curved waveguides and the problem of the field generated by a source in a parallel shear flow.

A multimodal formulation of the sound propagation in 2 or 3-dimensionnal curved waveguides is proposed and validated. Two infinite first-order differential equations are constructed for the pressure and axial velocity in the bend, as well as a Riccati equation for the impedance matrix. When the section of the bend is constant and the wall admittance is uniform, an algebraic formulation of the reflection and transmission matrices can be obtained, which enables us to characterize the scattering properties of bends and every complex duct system composed with curved and straight parts. A comparison between this wave approach and a scattering matrix constructed with a ray method shows a great similarity between these two results at high frequencies. Sound attenuation in lined bends is also considered using the multimodal method, and the properties of such ducts treated with absorbing materials are studied.

In a second part, the sound field generated by a source in duct carrying a shear flow is derived. We first derive the Green function of the Pridmore-Brown equation, governing modes in a rectilinear duct with shear flow. When applying the inverse Fourier transform, the poles of this Green function lead to the acoustic modes, which amplitude can then be calculated. The presence of a continuous spectra due to the singularity of the
Pridmore-Brown equation is also shown, and the contribution of corresponding continuum of hydrodynamic modes is evaluated.
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https://tel.archives-ouvertes.fr/tel-00007890
Contributor : Simon Félix <>
Submitted on : Monday, January 3, 2005 - 3:29:38 PM
Last modification on : Tuesday, March 31, 2020 - 3:20:49 PM
Long-term archiving on: : Friday, April 2, 2010 - 8:50:07 PM

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  • HAL Id : tel-00007890, version 1

Citation

Simon Félix. Propagation acoustique dans les guides d'ondes courbes et Problème avec source dans un écoulement cisaillé. Acoustique [physics.class-ph]. Université du Maine, 2002. Français. ⟨tel-00007890⟩

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