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Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence-aerofoil interaction noise

Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence-aerofoil interaction noise
Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence-aerofoil interaction noise
This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto 3D aerofoils. The influence on the noise reduction of the turbulence integral length-scale is also studied. An optimum serration wavelength is identified whereby maximum noise reductions are obtained, corresponding to when the transverse integral length-scale is roughly one-forth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number Sth=fh/U, where f, h and U are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil self-noise dominates the interaction noise. Leading edge serrations are also shown to reduce trailing edge self-noise. The mechanism for this phenomenon is explored through PIV measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.
0022-1120
435-464
Paruchuri, Chaitanya
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Joseph, Phillip
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Narayanan, Subramanyam
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Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Turner, Jacob
8618df92-3b0c-46e6-a482-dd12b261d9a7
Kim, Jae-Wook
fedabfc6-312c-40fd-b0c1-7b4a3ca80987
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052
Paruchuri, Chaitanya
5c1def64-6347-4be3-ac2d-b9f6a314b81d
Joseph, Phillip
9c30491e-8464-4c9a-8723-2abc62bdf75d
Narayanan, Subramanyam
ebf5b0fe-0c43-4544-8a34-6ba94c09c5e3
Vanderwel, Christina
fbc030f0-1822-4c3f-8e90-87f3cd8372bb
Turner, Jacob
8618df92-3b0c-46e6-a482-dd12b261d9a7
Kim, Jae-Wook
fedabfc6-312c-40fd-b0c1-7b4a3ca80987
Ganapathisubramani, Bharath
5e69099f-2f39-4fdd-8a85-3ac906827052

Paruchuri, Chaitanya, Joseph, Phillip, Narayanan, Subramanyam, Vanderwel, Christina, Turner, Jacob, Kim, Jae-Wook and Ganapathisubramani, Bharath (2017) Performance and mechanism of sinusoidal leading edge serrations for the reduction of turbulence-aerofoil interaction noise. Journal of Fluid Mechanics, 818, 435-464. (doi:10.1017/jfm.2017.141).

Record type: Article

Abstract

This paper presents the results of a detailed experimental investigation into the effectiveness of sinusoidal leading edge serrations on aerofoils for the reduction of the noise generated by the interaction with turbulent flow. A detailed parametric study is performed to investigate the sensitivity of the noise reductions to the serration amplitude and wavelength. The study is primarily performed on flat plates in an idealized turbulent flow, which we demonstrate captures the same behaviour as when identical serrations are introduced onto 3D aerofoils. The influence on the noise reduction of the turbulence integral length-scale is also studied. An optimum serration wavelength is identified whereby maximum noise reductions are obtained, corresponding to when the transverse integral length-scale is roughly one-forth the serration wavelength. This paper proves that, at the optimum serration wavelength, adjacent valley sources are excited incoherently. One of the most important findings of this paper is that, at the optimum serration wavelength, the sound power radiation from the serrated aerofoil varies inversely proportional to the Strouhal number Sth=fh/U, where f, h and U are frequency, serration amplitude and flow speed, respectively. A simple model is proposed to explain this behaviour. Noise reductions are observed to generally increase with increasing frequency until the frequency at which aerofoil self-noise dominates the interaction noise. Leading edge serrations are also shown to reduce trailing edge self-noise. The mechanism for this phenomenon is explored through PIV measurements. Finally, the lift and drag of the serrated aerofoil are obtained through direct measurement and compared against the straight edge baseline aerofoil. It is shown that aerodynamic performance is not substantially degraded by the introduction of the leading edge serrations on the aerofoil.

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jfm-serration_V10_rebuttal.pdf - Accepted Manuscript
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Accepted/In Press date: 8 February 2017
e-pub ahead of print date: 4 April 2017
Published date: 10 May 2017
Organisations: Acoustics Group, Engineering Science Unit

Identifiers

Local EPrints ID: 405336
URI: http://eprints.soton.ac.uk/id/eprint/405336
ISSN: 0022-1120
PURE UUID: 00f1e7f9-2cb4-490b-828a-6e6499ed0f29
ORCID for Christina Vanderwel: ORCID iD orcid.org/0000-0002-5114-8377
ORCID for Jacob Turner: ORCID iD orcid.org/0000-0002-0522-4340
ORCID for Jae-Wook Kim: ORCID iD orcid.org/0000-0003-0476-2574
ORCID for Bharath Ganapathisubramani: ORCID iD orcid.org/0000-0001-9817-0486

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Date deposited: 18 Feb 2017 00:23
Last modified: 28 Apr 2022 04:42

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Contributors

Author: Phillip Joseph
Author: Subramanyam Narayanan
Author: Jacob Turner ORCID iD
Author: Jae-Wook Kim ORCID iD

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