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Experimental study of noise emitted by circular cylinders with large roughness

Experimental study of noise emitted by circular cylinders with large roughness
Experimental study of noise emitted by circular cylinders with large roughness
The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe's roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.
0022-460X
6474-6497
Alomar, Antoni
8620bb97-69fb-4183-92b8-04b0e88a56f9
Angland, David
b86880c6-31fa-452b-ada8-4bbd83cda47f
Zhang, Xin
3056a795-80f7-4bbd-9c75-ecbc93085421
Molin, Nicolas
bd3c6c86-bbb5-4de1-87e0-1bbb4ce0fd21
Alomar, Antoni
8620bb97-69fb-4183-92b8-04b0e88a56f9
Angland, David
b86880c6-31fa-452b-ada8-4bbd83cda47f
Zhang, Xin
3056a795-80f7-4bbd-9c75-ecbc93085421
Molin, Nicolas
bd3c6c86-bbb5-4de1-87e0-1bbb4ce0fd21

Alomar, Antoni, Angland, David, Zhang, Xin and Molin, Nicolas (2014) Experimental study of noise emitted by circular cylinders with large roughness. Journal of Sound and Vibration, 333 (24), 6474-6497. (doi:10.1016/j.jsv.2014.07.013).

Record type: Article

Abstract

The aerodynamic noise generated by high Reynolds number flow around a bluff body with large surface roughness was investigated. This is a relevant problem in many applications, in particular aircraft landing gear noise. A circular cylinder in cross-flow and a zero-pressure-gradient turbulent boundary layer with various types of roughness was tested in a series of wind tunnel experiments. It has been shown that distributed roughness covering a circular cylinder affects the spectra over the entire frequency range. Roughness noise is dominant at high frequencies, and the peak frequency is well described by Howe's roughness noise model when scaled with the maximum outer velocity. There are differences between hemispherical and cylindrical roughness elements for both the circular cylinder and the zero-pressure-gradient turbulent boundary layer cases, indicating a dependence on roughness shape, not described by the considered roughness noise models. Cylindrical roughness generates higher noise levels at the highest frequencies, especially for the zero-pressure-gradient turbulent boundary layer case. Cable-type roughness aligned with the mean flow does not generate roughness noise, and its spectrum has been found to collapse with the smooth cylinder at medium and high frequencies. At low and medium frequencies the noise spectra have the same features as the smooth cylinder, but with higher shedding peak levels and fall-off levels, despite the decrease in spanwise correlation length. Roughness induces early separation, and thus a shift of the spectra to lower frequencies.

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Accepted/In Press date: 10 July 2014
e-pub ahead of print date: 22 August 2014
Published date: 2 December 2014
Organisations: Aerodynamics & Flight Mechanics Group

Identifiers

Local EPrints ID: 374771
URI: http://eprints.soton.ac.uk/id/eprint/374771
ISSN: 0022-460X
PURE UUID: cc5307a1-3a34-465c-9c6f-73c2371bba4b

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Date deposited: 02 Mar 2015 10:26
Last modified: 06 Jan 2021 17:30

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Contributors

Author: Antoni Alomar
Author: David Angland
Author: Xin Zhang
Author: Nicolas Molin

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