The Wavenumber-Phase Velocity Representation for the Turbulent Wall-Pressure Spectrum

Panton, Ronald L.; Robert, Gilles

doi:10.1115/1.2910301

Cited by 36 publications

(14 citation statements)

References 13 publications

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“…The map of a slice of the three-dimensional spectrum for k 3 = 0 As already observed by Wills (1970), Panton & Robert (1994), or Hu et al (2002, the convection ridge is asymmetric, with a tendency to broaden at higher frequencies. This broadening for increasing streamwise wavenumbers after the location of the convective peak is clearly noted in the individual spectra of figure 21, and is induced by the reduction of the correlation lengths at high frequencies.…”

Section: Wavenumber-frequency Spectramentioning

confidence: 57%

“…In experiments, the frequency spectra are generally obtained directly by Fourier transform of the signal at one point, but the wavenumber-frequency spectra are deduced from multipoint spacetime correlations, by using microphone arrays as in Panton & Robert (1994) …”

Section: Methods For Computing the Spectra And Resolution Characteristicsmentioning

confidence: 99%

“…The region |k| < κ 0 , where κ 0 = ω/c 0 is the acoustic wavenumber, is called the acoustic domain, and is more particularly the subject of the present study. The pressure fluctuations beneath a TBL have been the subject of numerous experimental and theoretical studies by Willmarth & Woolridge (1962), Bull (1967, Blake (1970), Wills (1970), Schewe (1983), Farabee & Casarella (1991), Panton & Robert (1994), Gravante et al (1998), Arguillat et al (2010), Ehrenfried & Koop (2008) among others (see the reviews by Willmarth (1975), or Blake (1986a)). With the development of supercomputers, the numerical simulation constitutes a new efficient approach.…”

Section: Wall Pressurementioning

confidence: 99%

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

Gloerfelt

Berland

2013

J. Fluid Mech.

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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.

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Section: Wavenumber-frequency Spectramentioning

confidence: 57%

Section: Methods For Computing the Spectra And Resolution Characteristicsmentioning

confidence: 99%

Section: Wall Pressurementioning

confidence: 99%

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

Gloerfelt

Berland

2013

J. Fluid Mech.

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“…This might induce an increase of the convective velocity u c , which affects the far-field noise. Since the far-field noise reduction is a function of frequency, u c is computed for all the points along the edge following a spectral approach (Panton & Robert 1994):…”

Section: Instantaneous and Mean Flow Organizationmentioning

confidence: 99%

Noise reduction mechanisms of sawtooth and combed-sawtooth trailing-edge serrations

Velden²,

et al. 2018

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Trailing-edge serrations are add ons retrofitted to wind-turbine blades to mitigate turbulent boundary-layer trailing-edge noise. This manuscript studies the physical mechanisms behind the noise reduction by investigating the far-field noise and the hydrodynamic flow field. A conventional sawtooth and a combed-sawtooth trailing-edge serration are studied. Combed-sawtooth serrations are obtained by filling the empty space between the teeth with combs (i.e. solid filaments). Both serration geometries are retrofitted to a NACA 0018 aerofoil at zero degree angle of attack. Computations are carried out by solving the explicit, transient, compressible lattice Boltzmann equation, while the acoustic far field is obtained by means of the Ffowcs Williams and Hawkings analogy. The numerical results are validated against experiments. It is confirmed that the combed-sawtooth serrations reduce noise more than the conventional sawtooth ones for the low-and mid-frequency range. It is found that the presence of combs affects the intensity of the scattered noise but not the frequency range of noise reduction. For both configurations, the intensity of the surface pressure fluctuations decreases from the root to the tip, and noise sources are mainly located at the serrations root for the low-and mid-frequency range. The presence of the filaments generates a more uniform distribution of the noise sources along the edges with respect to the conventional serration. The installation of combs mitigates the interaction between the two sides of the aerofoil at the trailing edge and the generation of a turbulent wake in the empty space between teeth. As a result, the inward (i.e. from the serration edge to the centreline) and outward (i.e. from the serration centreline to the edge) flow motions, due to the presence of the teeth, are mitigated. It is found that the installation of serrations affects the surface pressure fluctuations integral parameters. Both the spanwise correlation length and convective velocity of the surface pressure fluctuations increase with respect to the baseline straight configuration. When both quantities are similar to the one obtained for the straight trailing edge, the effect of the slanted edge is negligible, thus corresponding to no noise reduction. It is concluded that the changes in sound radiation are mainly caused by destructive interference of the radiated sound waves for which a larger spanwise correlation length is beneficial. Finally, the difference between measurements and the literature is caused by an incorrect modelling of the spanwise correlation † Email address for correspondence: F.Avallone@tudelft.nl Noise reduction mechanisms of sawtooth and combed-sawtooth trailing edges 561 length, which shows a different decay rate with respect to the one obtained for a straight trailing edge.

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“…Casademunt et al (1993) [7] did a numerical modeling on characterization and quantification of the adverse effects of time depending g-jitter. Panton and Robert (1994) [8] had transformed the cross-spectrum of wall pressure data from a wind tunnel to obtain the wave number frequency spectrum. Abraham and Keith (1995) [9] made a direct measurement of stream size wave number frequency spectra of turbulent wall pressure fluctuations made in an acoustically quiet water tunnel.…”

Section: Introductionmentioning

confidence: 99%