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A comparison with theory of peak to peak sound level for a model helicopter rotor generating blade slap at low tip speedsMini-tuft and smoke flow visualization techniques have been developed for the investigation of model helicopter rotor blade vortex interaction noise at low tip speeds. These techniques allow the parameters required for calculation of the blade vortex interaction noise using the Widnall/Wolf model to be determined. The measured acoustics are compared with the predicted acoustics for each test condition. Under the conditions tested it is determined that the dominating acoustic pulse results from the interaction of the blade with a vortex 1-1/4 revolutions old at an interaction angle of less than 8 deg. The Widnall/Wolf model predicts the peak sound pressure level within 3 dB for blade vortex separation distances greater than 1 semichord, but it generally over predicts the peak S.P.L. by over 10 dB for blade vortex separation distances of less than 1/4 semichord.
Document ID
19840032414
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Fontana, R. R.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Hubbard, J. E., Jr.
(MIT Cambridge, MA, United States)
Date Acquired
August 12, 2013
Publication Date
September 1, 1983
Subject Category
Aerodynamics
Accession Number
84A15201
Funding Number(s)
CONTRACT_GRANT: NAG2-182
CONTRACT_GRANT: NSG-1583
Distribution Limits
Public
Copyright
Other

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