Comparison of sound radiated by shallow cavities and backward facing steps

Jacob, Marc C.; Gradoz, Vincent; Louisot, Alain; Juvé, Daniel; Guerrand, Sylvie

doi:10.2514/6.1999-1892

Cited by 8 publications

(7 citation statements)

References 10 publications

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“…The simulations show a disturbance convection speed of 0.25 U for the wake mode and comparisons of the tones produced with those predicted by Rossiter's equation (K = 0. 25) give good agreement. The article includes pressure contours away from the cavity.…”

Section: Turbulence Modelingsupporting

confidence: 54%

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An overview of computational aeroacoustic techniques applied to cavity noise prediction

Grace

2001

39th Aerospace Sciences Meeting and Exhibit

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This report contains a summary of recent advances in the development of computational aeroacoustic methods for predicting the vibration and acoustics associated with grazing flow past cavities. The applications for which this flow field applies vary greatly and thus many Mach number regimes and cavity geometries are discussed. In addition to the computational developments, recent experimental studies are discussed. The results of many of these experiments can be used for validation of present and future prediction tools.

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Section: Turbulence Modelingsupporting

confidence: 54%

“…Jacob et al 25 A shallow cavity, L/D = 11, subject to low-speed flow was investigated in order to better understand the sound generated by the TGV's pantograph casing. Near-field and far-field acoustic measurements were made.…”

Section: Low Mach Number Flowsmentioning

confidence: 99%

An overview of computational aeroacoustic techniques applied to cavity noise prediction

Grace

2001

39th Aerospace Sciences Meeting and Exhibit

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“…Unlike the inter-coach gap, the pantograph recess has a large length-to depth ratio, and behaves aerodynamically as a 'closed' cavity, which corresponds to a typical ratio of L/D > 13. The shear layer developed from the incoming boundary layer separates at the cavity leading edge, and impinges on to the floor of the cavity [117,118], separating again before it reaches the trailing edge wall. The aerodynamic behaviour of closed cavities is similar to the flow over a pair of backward and forward facing steps, and is characterised by flow separation, and the wake developed in the separated regions.…”

Section: Pantograph Recessmentioning

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

118

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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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“…microphones located R 0 D 2:50 § 0:01 m away from a point C located 0.22 m downstream of the step (because the experiment is designed for a comparison with other ow con gurations 15 ). Their angle µ 0 with the downstream x direction varies from 30 to 150 § 2 deg (every 15 deg).…”

Section: Acoustic Measurementsmentioning

confidence: 99%

Experimental Study of Sound Generated by Backward-Facing Steps Under Wall Jet

et al. 2001

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Sound radiation by a backward facing step under a plane wall jet is examined. The investigation is based on an experiment where the mean velocity, the step heights, and the cross-stream extent of the jet are varied. The comparison between the backward-facing-step ow and the corresponding wall jet shows an acoustic source near the step. Both near-and far-eld measurements indicate how the step changes the radiation pattern of this source. The sound level is signi cantly increased into the upstream directions and accompanied by strong low-frequency peaks in the spectra. Aerodynamic results show that the reattachment length is much shorter for a step placed under a wall jet than for a step placed in a channel and that the most turbulent ow regions, namely, the jet mixing layer and the step reattachment region, coincide with the acoustic source locations. NomenclatureC = far-eld array center c 0 = speed of sound e = nozzle cross-stream width h = step height k = acoustic wave number l = jet half-width O = coordinate origin R = observation distance from O R 0 = observation distance from far eld array center C Re h = Reynolds number based step height h and maximal streamwise velocity at x D 0, U ref ; U ref h=º Re j = Reynolds number based on nozzle cross-stream width e and jet exhaust velocity U j ; U j e=º U; V = mean velocity in the x and y directions, respectively U j = jet outlet velocity U m = maximal streamwise velocity at a xed streamwise location U ref = maximal streamwise velocity at x D 0; U m .x D 0/ u; v = streamwise and cross-stream turbulent velocity uctuations u 0 ; v 0 = rms values of u and v X = streamwise distance from nozzle x = streamwise coordinate x r = x coordinate of the reattachment point y = cross ow coordinate y m = y location where U m is reached z = spanwise coordinate µ = observation angle with respect to (O; x )

show abstract

Comparison of sound radiated by shallow cavities and backward facing steps

Cited by 8 publications

References 10 publications

An overview of computational aeroacoustic techniques applied to cavity noise prediction

An overview of computational aeroacoustic techniques applied to cavity noise prediction

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

Experimental Study of Sound Generated by Backward-Facing Steps Under Wall Jet

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