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Details of Grant 

EPSRC Reference: GR/M85418/01
Title: TRANSONIC HELICOPTER NOISE
Principal Investigator: Dowling, Professor Dame A
Other Investigators:
Hynes, Dr TP Babinsky, Professor H Graham, Dr WR
Researcher Co-Investigators:
Project Partners:
Thales Ltd Westland
Department: Engineering
Organisation: University of Cambridge
Scheme: Standard Research (Pre-FEC)
Starts: 30 March 2000 Ends: 29 September 2003 Value (£): 180,458
EPSRC Research Topic Classifications:
Acoustics Aerodynamics
EPSRC Industrial Sector Classifications:
Aerospace, Defence and Marine
Related Grants:
Panel History:  
Summary on Grant Application Form
When helicopter blades move at high subsonic speeds patches of supersonic flow occur near the blades and these greatly influence the character and amplitude of the far-field sound. Traditional approaches either involve calculating a volume integral with high resolution or extending a CFD solution to a mid-field Kirchhoff surface. In both cases computational time can be prohibitive. Instead, we use an extension of the acoustic analogy based on a control surface which is chosen to be as small as possible, while enclosing the blade and any local patches of supersonic flow. The far-field sound can then be expressed solely in terms of mass and momentum fluxes through this control surface. We use CFD, with high resolution shock capturing techniques, to calculate the flow field near the blade. Particular emphasis will be placed on developing simple models to describe and explain dynamic changes in the acoustic sources in forward flight, thereby reducing CFD requirements by an order of magnitude. This near-field flow will be validated against transonic wind-tunnel and full-scale data. Predictions will be obtained for the far-field sound both in hover and in forward flight, and compared with measured pressures.
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Organisation Website: http://www.cam.ac.uk