Turbulent boundary-layer noise: direct radiation at Mach number 0.5

Abstract

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible.This is an author-deposited version published in: http://sam.ensam.eu Handle ID: .http://hdl.handle.net/10985/8636 To cite this version :Xavier GLOERFELT, Julien BERLAND -Turbulent boundary layer noise : direct radiation at Mach number 0.5 -Journal of Fluid Mechanics -Vol. 723, p.318-351 -2013 Any correspondence concerning this service should be sent to the repository Administrator : archiveouverte@ensam.euUnder consideration for publication in J. Fluid Mech. 1Turbulent boundary layer noise: direct radiation at Mach number 0.5 Boundary layers constitute a fundamental source of aerodynamic noise. A turbulent boundary layer over a plane wall can provide an indirect contribution to the noise by exciting the structure, and a direct noise contribution. The latter part can play a significant role even if its intensity is very low, explaining why it is hardly measured unambiguously.In the present study, the aerodynamic noise generated by a spatially developing turbulent boundary layer is computed directly by solving the compressible Navier-Stokes equations.This numerical experiment aims at giving some insight into the noise radiation character- The acoustic domain, corresponding to supersonic wavenumbers, is detectable but can † Present address: EDF R&D, MFEE, I84, 6 Quai Watier, 78400 Chatou, France. 2 X. Gloerfelt and J. Berlandhardly be separated from the convective ridge at this relatively high speed. This is also due to the low frequencies of sound emission as noted previously.

An experimental characterisation of wall pressure wavevector-frequency spectra in the presence of pressure gradients

“…Mainly the incompressible part of spectra has been reported over the past fifty years [8,33]. It must be also mentioned that these difficulties are also encountered in numerical simulations [24,30,32]. Second, zeropressure-gradient turbulent boundary layers are often considered.…”

The influence of a pressure wavepacket's characteristics on its acoustic radiation

“…The increase of the acoustic efficiency with M c and M 1 follows what was expected from the analytical result [Eq. (23)]. The previous conclusions regarding the phase Mach number M c effects on efficiency still hold for a moving medium, that is, at a given length, the higher M c , the higher efficiency [ Fig.…”

“…It thus broadens possibilities toward flows where organized, unsteady motions may be identified as dominant aeroacoustic sources such as cavities 22 and turbulent boundary layers. 23 The paper is organized as follow: Section II explicits the theoretical background with the mathematical conventions hereby adopted for the resolution of the wave equation; the Kirchhoff formalism is introduced in a static, propagation medium and a formulation for a distant observer is given. Analytical developments yielded prediction for high efficiency conditions; the numerical tool is presented in Sec.…”

An acoustic model of a Helmholtz resonator under a grazing turbulent boundary layer

“…Measurements which are based on only a few microphones are incorrect, due to the known frequency and scale dependencies (i.e. streamwise probe separation) of the convection velocity [26,29]. Integral definitions of the convection velocity like in Alamo and Jiménez [23] are not recommended in the present case of a distorted TBL since the convective ridge does not decay rapidly at high |k x | or ω.…”