Laboratoire de Mécanique des Fluides et d'Acoustique - UMR 5509

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Accueil > Actualités > Séminaires > Archives 2018

Xavier Gloerfelt – Laboratoire DynFluid – ENSAM Arts et Métiers ParisTech

A numerical experiment on boundary layer noise

Vendredi 16 Novembre 2018, 11h - Salle 17 - Bât. W1bis !! - ECL

 A numerical experiment on boundary layer noise

Excitation of the walls of a vehicle by turbulent boundary layers (TBL) constitutes a major source of interior noise. The random character of the wall pressure distribution induced by the boundary layer has a major effect on the induced noise and its cross-spectral density, or equivalently its representation in the wavenumber-frequency space, plays a major role in determining the effective force causing motion to the structure. This topic has been widely studied in the past and several models of wall pressure spectra have been proposed based on experiments in air and water. The hydrodynamic pressure at the wall is dominated by the convective motions of turbulent structures in the boundary layer, which is well-known and satisfactorily represented by Taylor’s hypothesis. The region of low wavenumbers, sometimes called subconvective and comprising supersonic wavenumbers (acoustic waves) is very hard to characterize unambiguously in experiments because of their very low levels compared to the convective motions. These large-wavelength fluctuations are however of great interest since the coupling with wall vibrations is most effective in this range.
We will present a new way of characterizing this important TBL excitation by using numerical experiments based on direct noise computation. Accessing the acoustic radiation from the TBL allows a characterization of pressure excitation encompassing the acoustic wavenumbers and the subconvective range up to the convective motions. It is interesting to analyse these fluctuations and to link them with large-scale motions in the TBL.


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