On the generation of discrete frequency tones by the flow around an aerofoil


McAlpine, Alan, Nash, E.C. and Lowson, M.V. (1999) On the generation of discrete frequency tones by the flow around an aerofoil. Journal of Sound and Vibration, 222, (5), 753-779. (doi:10.1006/jsvi.1998.2085).

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Description/Abstract

Tonal noise, the self-induced discrete frequency noise generated by aerofoils, is investigated. It is heard from an aerofoil placed in streams at low Mach number flows when inclined at a small angle to the stream. It is a piercing whistle, commonly up to 30 dB above the background noise level. Previous authors have attributed tonal noise to a feedback loop consisting of a coupling between laminar boundary-layer instability waves and sound waves propagating in the free stream. Boundary-layer measurements have shown the presence of tonal noise is closely related to the existence of a region of separated flow close to the trailing edge of the aerofoil. An analysis of the linear stability of the boundary-layer flow over the aerofoil is presented. The amplification of the instability waves is shown to be controlled almost entirely by the region of separated flow close to the trailing edge. In light of these new experimental and theoretical results the suitability of the aero-acoustic feedback model is discussed.

Item Type: Article
ISSNs: 0022-460X (print)
Related URLs:
Subjects: T Technology > T Technology (General)
Divisions: University Structure - Pre August 2011 > Institute of Sound and Vibration Research > Fluid Dynamics and Acoustics
ePrint ID: 147669
Date Deposited: 17 Jun 2010 14:00
Last Modified: 27 Mar 2014 19:08
URI: http://eprints.soton.ac.uk/id/eprint/147669

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