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Model rotor low frequency broadband noise at moderate tip speedsThe results of an experimental investigation of low frequency broadband noise (LFBN) radiated from model helicopter rotors are presented. The results are for a range of tip Mach numbers (Mt) up to 0.50. The effect of rotor blade loading, advance ratio, tip speed, number of blades and free stream turbulence on the sound pressure level (SPL) and the spectrum of LFBN have been investigated. The peak SPL of LFBN appears to follow an M(4) law if the effect of rms turbulence velocity is removed. The peak SPL of LFBN seems to saturate with increases in advance ratio and with blade loading, and is proportional to the square of the turbulence integral scale when the effect of rms turbulence velocity and Mt are removed. Also, a simple peak SPL scaling law for noise from a helicopter rotor in forward flight due to convected sinusoidal gust is developed. The trend predicted by this scaling law is found to be satisfactory for the variation of the peak SPL of LFBN with tip speed.
Document ID
19800051801
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Humbad, N. G.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Harris, W. L.
(MIT Cambridge, Mass., United States)
Date Acquired
August 10, 2013
Publication Date
June 1, 1980
Subject Category
Acoustics
Report/Patent Number
AIAA PAPER 80-1013
Meeting Information
Meeting: Aeroacoustics Conference
Location: Hartford, CT
Start Date: June 4, 1980
End Date: June 6, 1980
Sponsors: American Institute of Aeronautics and Astronautics
Accession Number
80A35971
Funding Number(s)
CONTRACT_GRANT: NSG-1583
Distribution Limits
Public
Copyright
Other

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