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An analytic solution for the noise generated by gust-aerofoil interaction for plates with serrated leading edges

An analytic solution for the noise generated by gust-aerofoil interaction for plates with serrated leading edges
An analytic solution for the noise generated by gust-aerofoil interaction for plates with serrated leading edges
This paper presents an analytic solution for the sound generated by an unsteady gust interacting with a semi-infinite flat plate with a serrated leading edge in a background steady uniform flow. Viscous and non-linear effects are neglected. The Wiener-Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to permit analytical progress. The solution is obtained in terms of a modal expansion in the spanwise coordinate, however for low- and mid-range incident frequencies only the zeroth order mode is seen to contribute to the far-field acoustics, therefore the far-field noise can be quickly evaluated. The solution gives insight into the potential mechanisms behind the reduction of noise for plates with serrated leading edges compared to those with straight edges, and predicts a logarithmic dependence between the tip-to-root serration height and the decrease of far-field noise. The two mechanisms behind the noise reduction are proposed to be an increased destructive interference in the far field, and a redistribution of acoustic energy from low cut-on modes to higher cutoff modes as the tip-to-root serration height is increased. The analytic results show good agreement in comparison with experimental measurements. The results are also compared against non-linear numerical predictions where good agreement is also seen between the two results as frequency and tip-to-root ratio are varied.
0022-1120
515-536
Ayton, Lorna J.
58d53540-2704-4eaa-acfc-dcaee78637ac
Kim, Jae
fedabfc6-312c-40fd-b0c1-7b4a3ca80987
Ayton, Lorna J.
58d53540-2704-4eaa-acfc-dcaee78637ac
Kim, Jae
fedabfc6-312c-40fd-b0c1-7b4a3ca80987

Ayton, Lorna J. and Kim, Jae (2018) An analytic solution for the noise generated by gust-aerofoil interaction for plates with serrated leading edges. Journal of Fluid Mechanics, 853, 515-536. (doi:10.1017/jfm.2018.583).

Record type: Article

Abstract

This paper presents an analytic solution for the sound generated by an unsteady gust interacting with a semi-infinite flat plate with a serrated leading edge in a background steady uniform flow. Viscous and non-linear effects are neglected. The Wiener-Hopf method is used in conjunction with a non-orthogonal coordinate transformation and separation of variables to permit analytical progress. The solution is obtained in terms of a modal expansion in the spanwise coordinate, however for low- and mid-range incident frequencies only the zeroth order mode is seen to contribute to the far-field acoustics, therefore the far-field noise can be quickly evaluated. The solution gives insight into the potential mechanisms behind the reduction of noise for plates with serrated leading edges compared to those with straight edges, and predicts a logarithmic dependence between the tip-to-root serration height and the decrease of far-field noise. The two mechanisms behind the noise reduction are proposed to be an increased destructive interference in the far field, and a redistribution of acoustic energy from low cut-on modes to higher cutoff modes as the tip-to-root serration height is increased. The analytic results show good agreement in comparison with experimental measurements. The results are also compared against non-linear numerical predictions where good agreement is also seen between the two results as frequency and tip-to-root ratio are varied.

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Accepted/In Press date: 23 July 2018
e-pub ahead of print date: 23 August 2018
Published date: 25 October 2018

Identifiers

Local EPrints ID: 424403
URI: http://eprints.soton.ac.uk/id/eprint/424403
ISSN: 0022-1120
PURE UUID: 9ce95e11-af55-48e1-a49d-b86e2950128f
ORCID for Jae Kim: ORCID iD orcid.org/0000-0003-0476-2574

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Date deposited: 05 Oct 2018 11:36
Last modified: 14 Mar 2019 05:03

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