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Development of a noncompact source theory with applications to helicopter rotorsA new formulation for determining the acoustic field of moving bodies, based on acoustic analogy, is derived. The acoustic pressure is given as the sum of two integrals, one of which has a derivative with respect to time. The integrands are functions of the normal velocity and surface pressure of the body. A computer program based on this formulation was used to calculate acoustic pressure signatures for several helicoptor rotors from experimental surface pressure data. Results are compared with those from compact source calculations. It is shown that noncompactness of steady sources on the rotor can account for the high harmonics of the pressure system. Thickness noise is shown to be a significant source of sound, especially for blunt airfoils in regions where noncompact source theory should be applied.
Document ID
19760055113
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Farassat, F.
(NASA Langley Research Center Hampton, VA, United States)
Brown, T. J.
(NASA Langley Research Center Hampton, Va., United States)
Date Acquired
August 8, 2013
Publication Date
July 1, 1976
Subject Category
Acoustics
Report/Patent Number
AIAA PAPER 76-563
Meeting Information
Meeting: Aero-Acoustics Conference
Location: Palo Alto, CA
Start Date: July 20, 1976
End Date: July 23, 1976
Sponsors: American Institute of Aeronautics and Astronautics
Accession Number
76A38079
Funding Number(s)
CONTRACT_GRANT: NGR-09-010-085
Distribution Limits
Public
Copyright
Other

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