Characterization of an acoustic liner by means of Laser Doppler Velocimetry in a subsonic flow

Minotti, Angelot; Simon, Frank; Gantié, F.

doi:10.1016/j.ast.2007.09.007

Cited by 43 publications

(29 citation statements)

References 17 publications

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“…This post-processing is based on the hypothesis that acoustic phenomena are totally uncorrelated with turbulence phenomena and electronic noises. It consists in working in frequency domain and using a reference signal: the acoustic particle velocity is then the measured fluctuation velocity correlated with the reference microphone signal: [16][17][18] …”

Section: Acoustic Velocity Extractionmentioning

confidence: 99%

“…Optical measurements are used to obtain acoustic and aerodynamic fields in the hologram plane. Laser Doppler Velocimetry (LDV), which can provide acoustic velocity from measured instantaneous velocity using a specific postprocessing technique, [16][17][18] has been chosen. Thus, this paper is especially focused on velocity-based propagators.…”

Section: And Sourcesmentioning

confidence: 99%

“…16 Here a specific signal post-processing, adapted to particles which arrive randomly, is used to extract the acoustic particle velocity from LDV measurements. This post-processing is based on the hypothesis that acoustic phenomena are totally uncorrelated with turbulence phenomena and electronic noises.…”

Section: Acoustic Velocity Extractionmentioning

confidence: 99%

“…pðr; xÞ ¼ F À1 fF ½u n ðr 0 ; xÞ F ½G up b ðrjr 0 ; xÞg; (16) pðr; xÞ ¼ F À1 fF ½pðr 0 ; xÞ F ½G pp b ðrjr 0 ; xÞg;…”

Section: Real Convective Spatial Propagatorsunclassified

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Non-intrusive planar velocity-based nearfield acoustic holography in moving fluid medium

Parisot-Dupuis¹,

Simon²,

Piot³

et al. 2013

The Journal of the Acoustical Society of America

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Nearfield Acoustic Holography (NAH) is a powerful acoustic imaging method, but its application in aeronautics can be limited by intrusive measurements of acoustic field. In this paper, a moving fluid medium NAH procedure using non-intrusive velocity measurements is proposed. This method is based on convective Kirchhoff-Helmholtz integral formula. Convective equations and convective Green's function are used to derive convective real-space propagators including airflow effects. Discrete Fourier transforms of these propagators allow the assessment of acoustic fields from acoustic pressure or normal acoustic velocity measurements. As the aim is to derive an in-flow velocity-based NAH method, this study is especially focused on real convective velocity-to-pressure propagator. In order to validate this procedure, simulations in the case of monopole sources radiating in various uniform subsonic flows have been performed. NAH provides very favorable results when compared to the simulated fields. A comparison of results obtained by the real propagator and those obtained by the wave number-frequency-domain one developed by Kwon et al. [J. Acoust. Soc. Am. 128(4), 1823-1832 (2010)] shows the interest of using the real-form in the case of pressure backward propagation from velocity measurements. The efficiency of the developed procedure is confirmed by a wind tunnel campaign with a flush-mounted loudspeaker and non-intrusive Laser Doppler Velocimetry velocity measurements.

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Section: Acoustic Velocity Extractionmentioning

confidence: 99%

Section: And Sourcesmentioning

confidence: 99%

Section: Acoustic Velocity Extractionmentioning

confidence: 99%

“…pðr; xÞ ¼ F À1 fF ½u n ðr 0 ; xÞ F ½G up b ðrjr 0 ; xÞg; (16) pðr; xÞ ¼ F À1 fF ½pðr 0 ; xÞ F ½G pp b ðrjr 0 ; xÞg;…”

Section: Real Convective Spatial Propagatorsunclassified

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Non-intrusive planar velocity-based nearfield acoustic holography in moving fluid medium

Parisot-Dupuis¹,

Simon²,

Piot³

et al. 2013

The Journal of the Acoustical Society of America

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“…It can be educed from the extraneous noise (mainly due to the turbulent flow) by a technique similar to the three-microphone signal enhancement technique. 16,18 It consists in calculating the cross-spectral density function G Vi ,ls between the velocity signal V i and the loudspeaker signal ls (see 17,19,20 ). The auto-spectral density function of the acoustic velocity reads:…”

Section: Iic2 Onera B2a Ductmentioning

confidence: 99%

ONERA-NASA cooperative effort on liner impedance eduction

Primus

Piot²,

Simon³

et al. 2013

19th AIAA/CEAS Aeroacoustics Conference

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As part of a cooperation between ONERA and NASA, the liner impedance eduction methods developed by the two research centers are compared. The NASA technique relies on an objective function built on acoustic pressure measurements located on the wall opposite the test liner, and the propagation code solves the convected Helmholtz equation in uniform flow using a finite element method that implements a continuous Galerkin discretization. The ONERA method uses an objective function based either on wall acoustic pressure or on acoustic velocity acquired above the liner by Laser Doppler Anemometry, and the propagation code solves the linearized Euler equations by a discontinuous Galerkin discretization. Two acoustic liners are tested in both ONERA and NASA flow ducts and the measured data are treated with the corresponding impedance eduction method. The first liner is a wire mesh facesheet mounted onto a honeycomb core, designed to be linear with respect to incident sound pressure level and to grazing flow velocity. The second one is a conventional, nonlinear, perforate-over-honeycomb single layer liner. Configurations without and with flow are considered. For the nonlinear liner, the comparison of liner impedance educed by NASA and ONERA shows a sensitivity to the experimental conditions, namely to the nature of the source and to the sample width.

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Multi-scale measurement of acoustic particle velocity and flow velocity for liner investigations

et al. 2013

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Characterization of an acoustic liner by means of Laser Doppler Velocimetry in a subsonic flow

Cited by 43 publications

References 17 publications

Non-intrusive planar velocity-based nearfield acoustic holography in moving fluid medium

Non-intrusive planar velocity-based nearfield acoustic holography in moving fluid medium

ONERA-NASA cooperative effort on liner impedance eduction

Multi-scale measurement of acoustic particle velocity and flow velocity for liner investigations

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