Numerical validation of shear flow corrections for beamforming acoustic source localisation in open wind-tunnels

Padois, Thomas; Prax, Christian; Valeau, Vincent

doi:10.1016/j.apacoust.2012.09.013

Cited by 48 publications

(20 citation statements)

References 19 publications

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“…No flow correction is taking into account due to the low velocity and small flow thickness. 39 Usually, the beamforming assumes a scan zone, where the sources are searched, in a plane parallel to the microphone array close to the profile. In this case, the scan zone is the profile to be more accurate.…”

Section: Acoustic Source Localization With a Microphone Arraymentioning

confidence: 99%

Detailed experimental investigation of the aeroacoustic field around a Controlled-Diffusion airfoil

Padois

Laffay

Idier

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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This study presents the first set of experiments with the Controlled-Diffusion (CD) airfoil in the newly-built anechoic wind-tunnel at Université de Sherbrooke. Velocity measurements in the latter show very uniform mean flow and low turbulence level (0.4 %) up to 56 m/s in the 30 cm square nozzle exit section. Acoustic and velocity measurements have been carried out at several flow velocities and angles of attack. Three distinct flow regimes are observed. At high angle of attack and high velocity the usual broadband noise signature found in the Ecole Centrale de Lyon anechoic wind tunnels is recovered. At low angle of attack, the power spectral density of the microphone signal is dominated by a primary tone with secondary tones, typical of Tollmien-Schlichting noise radiation. This dominant tone is also recovered in the power spectral density of the flow velocity signal. Signal processing tools (spectrogram and bicoherence) are used to investigate the presence of the secondary tones. Two tonal regimes can then be distinguished: one stationnary and one intermittent where some tones disappear intermittently and are formed by a non-linear process. Finally, two parallel microphone arrays associated with high resolution imaging is used to localize the noise sources at the primary tone frequency, which are found at the airfoil trailing edge. At this low frequency, the L1-GIB algorithm is clearly seen more efficient than classical beamforming.

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Section: Acoustic Source Localization With a Microphone Arraymentioning

confidence: 99%

Detailed experimental investigation of the aeroacoustic field around a Controlled-Diffusion airfoil

Padois

Laffay

Idier

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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“…Consisting in numerical simulations relying on a Computational AeroAcoustics (CAA) approach, these studies made it possible, first, to evaluate and, then, to discriminate the diverse acoustic installation effects to be possibly induced by the facility components (e.g., mounting side plates, nozzle, collector plate) or features (e.g., confined jet vs. co-flow) onto airframe noise experiments that are usually conducted within QFF (3)(4)(5)(6). At the light of these studies, it appeared that, although they were rather modest compared to the reflection / diffraction effects inherited from the experimental apparatus, the refraction effects resulting from the facility jet flow might impact the noise propagation in a non-negligible way, for instance by altering importantly the acoustic phase -a thing that could question the application of array localization techniques within facility environments (7). Inter-noise 2014 Therefore, follow-on computations were recently achieved on the basis of these previous works, with the view of investigating more closely the sole refraction effects to be expected from the jet flow of typical anechoic facilities such as NASA's LaRC QFF.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation of the Refraction Effects by Jet Flows in Anechoic Wind Tunnels, with Application to NASA/LaRC Quiet Flow Facility

Redonnet¹,

Bulté²

2015

21st AIAA/CEAS Aeroacoustics Conference

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In regard to the problem of aircraft noise mitigation, the present study focuses on the refraction effects to be possibly induced by anechoic facility jet flows on the measured acoustic signatures, during typical airframe noise experiments. To this end, Computational AeroAcoustics (CAA) calculations based on the solving of the Perturbed Euler Equations (PEE) are conducted, enabling the estimation of the refraction effects characterizing a typical open-jet, anechoic wind tunnel, namely the NASA Langley's Quiet Flow Facility (QFF). Coming along with their validation against analytical results obtained through a Ray Tracing (RT) technique, the analysis of these CAA/PEE calculations highlights the refraction effects by the facility jet flow, delivering preliminary insights about what are the key parameters (jet height, jet curvature, jet spreading angle, shear layer thickness, etc.) to play a major role in these refraction phenomena.

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“…differences in propagation time due to the acoustics waves travelling through the shear layer, were taken into account using an approximate method based on the analysis of Padois et al [29]. In that study, it was shown that for a monopole source located inside a shear layer, the delay-and-sum beamforming image will be shifted downstream by a distance x sh ¼ Mh, where M is the Mach number of the flow and h is the perpendicular distance from the source to the shear layer.…”

Section: Experimental Test Cases and Methodsmentioning

confidence: 99%

Three-dimensional beamforming of dipolar aeroacoustic sources

Porteous

Prime

Doolan

et al. 2015

Journal of Sound and Vibration

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a b s t r a c tThis paper outlines and compares four beamforming algorithms for accurately localising acoustic dipole sources in a three-dimensional domain, such as noise sources produced by flow-body interaction. These algorithms include conventional cross-spectral beamforming, conventional beamforming with deconvolution via CLEAN-SC, 'multiplicative' crossspectral beamforming and multiplicative beamforming with CLEAN-SC. The latter two algorithms are novel to the field of aeroacoustics and rely on the mutual cancellation of spatially incoherent sources between orthogonally aligned microphone arrays to improve the quality of the source map. The algorithms were used on both synthetic and experimental data. By comparing the performance of each algorithm in terms of source localisation accuracy, source strength estimation and resolution, it was found that conventional beamforming with CLEAN-SC is the preferred method for beamforming aeroacoustic sources in three dimensions, albeit at a higher computational cost than the other three. The results also showed that multiplicative beamforming methods give source maps that are more interpretable than conventional cross-spectral beamforming methods at no extra computational expense.

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Numerical validation of shear flow corrections for beamforming acoustic source localisation in open wind-tunnels

Cited by 48 publications

References 19 publications

Detailed experimental investigation of the aeroacoustic field around a Controlled-Diffusion airfoil

Detailed experimental investigation of the aeroacoustic field around a Controlled-Diffusion airfoil

Numerical Investigation of the Refraction Effects by Jet Flows in Anechoic Wind Tunnels, with Application to NASA/LaRC Quiet Flow Facility

Three-dimensional beamforming of dipolar aeroacoustic sources

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