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The evolution of methods for noise prediction of high speed rotors and propellers in the time domainLinear wave equation models which have been used over the years at NASA Langley for describing noise emissions from high speed rotating blades are summarized. The noise sources are assumed to lie on a moving surface, and analysis of the situation has been based on the Ffowcs Williams-Hawkings (FW-H) equation. Although the equation accounts for two surface and one volume source, the NASA analyses have considered only the surface terms. Several variations on the FW-H model are delineated for various types of applications, noting the computational benefits of removing the frequency dependence of the calculations. Formulations are also provided for compact and noncompact sources, and features of Long's subsonic integral equation and Farassat's high speed integral equation are discussed. The selection of subsonic or high speed models is dependent on the Mach number of the blade surface where the source is located.
Document ID
19870024496
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Farassat, F.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1986
Subject Category
Acoustics
Accession Number
87A11770
Distribution Limits
Public
Copyright
Other

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