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Sensitivity of acoustic predictions to variation of input parametersThe noise prediction code WOPWOP predicts the thickness and loading noise produced by a helicopter rotor, given the blade motion, rotor operating conditions, and fluctuating force distribution over the blade surface. However, the criticality of these various inputs, and their respective effects on the predicted acoustic field, have never been fully addressed. This paper examines the importance of these inputs, and the sensitivity of the acoustic predictions to a variation of each parameter. The effects of collective and cyclic pitch, as well as coning and flapping, are presented. Blade loading inputs are examined to determine the necessary spatial and temporal resolution, as well as the importance of the cordwise distribution. The acoustic predictions show regions in the acoustic field where significant errors occur when simplified blade motions or blade loadings are used. An assessment of the variation in the predicted acoustic field is balanced by a consideration of CPU time necessary for the various approximations.
Document ID
19930045407
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Brentner, Kenneth S.
(NASA Langley Research Center Hampton, VA, United States)
Marcolini, Michael A.
(NASA Langley Research Center Hampton, VA, United States)
Burley, Casey L.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 16, 2013
Publication Date
January 1, 1991
Publication Information
Publication: In: AHS and Royal Aeronautical Society, Technical Specialists' Meeting on Rotorcraft Acoustics(Fluid Dynamics, Philadelphia, PA, Oct. 15-17, 1991, Proceedings (A93-29401 10-71)
Publisher: American Helicopter Society
Subject Category
Acoustics
Accession Number
93A29404
Distribution Limits
Public
Copyright
Other

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