Beamforming-Based Noise Level Measurements in Hard-Wall Closed-Section Wind Tunnels

Davy, Renaud

doi:10.2514/6.2012-2226

Cited by 18 publications

(10 citation statements)

References 13 publications

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“…This, together with the sound reflections from the tunnel walls, can adversely affect the quality of the data acquired. This can be overcome to some extent by using advanced microphone array techniques [35][36][37]. The microphone array can be flush-mounted with the wall or floor to prevent excitation of the microphones by the flow.…”

Section: Types Of Wind Tunnelmentioning

confidence: 99%

Recent developments in the prediction and control of aerodynamic noise from high-speed trains

Thompson

Iglesias

Liu

et al. 2015

International Journal of Rail Transportation

112

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At speeds above 300-350 km/h, the main source of noise from trains is the aerodynamic noise caused by the air flow over the train structure. The sound level increases with train speed at a rate of between 60 and 80 times the logarithm of the speed so that, as speeds increase further, the noise increases dramatically. The main aerodynamic noise is produced by the air flow passing over the pantograph, the train nose, the bogie region and cavities such as the pantograph recess and the inter-coach gap. Experimental and numerical methods for studying aerodynamic noise are reviewed including the use of microphone arrays, wind tunnels, computational fluid dynamics and semi-empirical methods. Potential mitigation measures that can control aerodynamic noise are also reviewed.

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Section: Types Of Wind Tunnelmentioning

confidence: 99%

Recent developments in the prediction and control of aerodynamic noise from high-speed trains

Thompson

Iglesias

Liu

et al. 2015

International Journal of Rail Transportation

112

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“…The array is composed of 120 Bruël and Kjaer's 4138 1/4 inch microphones forming 7 arms over a length of about 0.8 m . 11 The microphones are protected from the turbulent boundary-layer by a thin flush-mounted metallic cloth. The signals are synchronously recorded with a commercial 2 × 24-bits B&K LanXI system at 131,072 Hz sampling frequency for about 24 s.…”

Section: Wind Tunnel and Microphone Array Measurementsmentioning

confidence: 99%

“…Given the interest of performing reliable acoustic measurements in aerodynamic wind tunnels, many efforts have been made for years to reduce the background noise in closed test sections 1, 2, 3 , to improve inflow acoustic measurements 4,5 and to develop data dereverberation techniques 6,7,8 . In particular, beamforming techniques based on the free-field Green's function may be able to provide noise source levels in reverberating test sections 9,10,11,12 . Dereverberation is indeed achieved through the focusing performance of beamforming, that enables to spatially separate real acoustic sources within the test section and their images located outside the test section 9,11 .…”

Section: Introductionmentioning

confidence: 99%

“…In particular, beamforming techniques based on the free-field Green's function may be able to provide noise source levels in reverberating test sections 9,10,11,12 . Dereverberation is indeed achieved through the focusing performance of beamforming, that enables to spatially separate real acoustic sources within the test section and their images located outside the test section 9,11 . The acoustic level is then determined with a deconvolution technique, by integrating the level of the real sources in the test section only.…”

Section: Introductionmentioning

confidence: 99%

“…Specifically, acoustic maps obtained for a single theoretical monopole and a line source in the reverberating test section are presented. The analytical microphone array data are computed with the image noise source theory 15,11 . The experimental noise data on the rod and the airfoil are analyzed in Sec.…”

Section: Introductionmentioning

confidence: 99%

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2D high-lift airfoil noise measurements in an aerodynamic wind tunnel

Bahr¹,

Humphreys²,

Ernst³

et al. 2015

21st AIAA/CEAS Aeroacoustics Conference

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In the frame of the common project LEISA2 between ONERA and DLR, a 2D high-lift airfoil model of DLR was tested both in the ONERA's F2 aerodynamic wind tunnel and in the DLR's AWB anechoic wind tunnel. A large aeroacoustic database was collected. The present paper is concerned with the assessment of acoustic data in F2. The question of performing accurate noise level measurements in spite of the acoustic reflections in the test section is adressed in particular. The measurement technique relies on beamforming methodologies. The noise sources on the airfoil are firstly analyzed with the conventional beamforming technique, based on the free-field Green's function. A deconvolution algorithm is then applied to determine the acoustic level of the sources. To assess the results in F2, the deconvolved noise source levels are finally compared with noise spectra measurements in AWB. High-amplitude tones are observed and the corresponding noise sources are identified on the slat. The tone levels are imperfectly recovered yet. On the other hand, broadband noise levels are deemed in fair agreement between F2 and AWB. The broadband noise sources are identified both on the slat and the flap.f frequency C P static pressure coeff.: C P = P −P∞ 0.5ρ∞U 2 ∞ P local static pressure α F2 angle of incidence in F2 P ∞ static pressure at infinity α AWB angle of incidence in AWB U ∞ mean velocity at infinity ∆ spatial resolution of the scanning points ρ ∞ mean mass density at infinity

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