Experimental investigation of surface roughness generated flow noise

Hersh, A. S.

doi:10.2514/6.1983-786

Cited by 21 publications

(26 citation statements)

References 8 publications

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“…Fig. 4 Roughness noise spectra predicted by the empirical model and numerical integration together with the experimental data by Hersh [15].…”

Section: B Direct Numerical Integrationmentioning

confidence: 99%

“…where the empirical coefficients, 0 , , and n, are partially estimated by the experimental data of Hersh [15] on sound radiation by sandroughened pipes of various grit sizes. The best fit to Hersh's data can be achieved by taking 0:0025; n 11…”

Section: Evaluation Of the Rough-wall Acoustic Pressure Spectrummentioning

confidence: 99%

“…An empirical formula for P R x; ! was also proposed by Howe [14] and the values of adjustable coefficients were partially estimated using the experimental data of Hersh [15] on the sound radiation by sand-roughened pipes of various grit sizes. However, not all the coefficient values have been determined yet due to insufficient experimental data; hence the absolute level of P R x; !…”

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confidence: 99%

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Assessment of the Contribution of Surface Roughness to Airframe Noise

Liu

Dowling

2007

AIAA Journal

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The generation of sound by turbulent boundary-layer flow at low Mach number over a rough wall is investigated by applying a theoretical model that describes the scattering of the turbulence near field into sound by roughness elements. Attention is focused on the numerical method to approximately quantify the absolute level of far-field radiated roughness noise. Models for the source statistics are obtained by scaling smooth-wall data by the increased skin friction velocity and boundary-layer thickness for a rough surface. Numerical integration is performed to determine the roughness noise, and it reproduces the spectral characteristics of the available empirical formula and experimental data. Experiments are conducted to measure the radiated sound from two rough plates in an open jet. The measured noise spectra of the rough plates are above that of a smooth plate in 1-2.5 kHz frequency and exhibit reasonable agreement with the predicted level. Estimates of the roughness noise for a Boeing 757 sized aircraft wing with idealized levels of surface roughness show that in the high-frequency region the sound radiated from surface roughness may exceed that from the trailing edge, and higher overall sound pressure levels are observed for the roughness noise. The trailing edge noise is also enhanced by surface roughness somewhat. A parametric study indicates that roughness height and roughness density significantly affect the roughness noise with roughness height having the dominant effect. The roughness noise directivity varies with different levels of surface roughness.

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“…Fig. 4 Roughness noise spectra predicted by the empirical model and numerical integration together with the experimental data by Hersh [15].…”

Section: B Direct Numerical Integrationmentioning

confidence: 99%

Section: Evaluation Of the Rough-wall Acoustic Pressure Spectrummentioning

confidence: 99%

mentioning

confidence: 99%

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Assessment of the Contribution of Surface Roughness to Airframe Noise

Liu

Dowling

2007

AIAA Journal

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“…Howe evaluated P R (ω) by means of a conventional asymptotic approximation [1,3] based on P s (κ, ω) being sharply peaked in the vicinity of the convective ridge. He also proposed empirical models [3][4][5] for P R (ω) by curve-fitting available experimental data of Hersh [6]. The empirical coefficients were partially estimated, but not all the coefficient values could be determined due to the lack of directivity information in Hersh's data.…”

Section: Introductionmentioning

confidence: 99%

“…Measurement of roughness noise is difficult as it can be easily contaminated due to its very low spectral levels. Hersh [6] studied the radiation of sound from sand-roughened pipes of various grit sizes. He concluded through measurements that the 6th power variation of the overall sound pressure level with flow velocity suggests a dipole source.…”

Section: Introductionmentioning

confidence: 99%