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Helicopter model rotor-blade vortex interaction impulsive noise: Scalability and parametric variationsAcoustic data taken in the anechoic Deutsch-Niederlaendischer Windkanal (DNW) have documented the blade vortex interaction (BVI) impulsive noise radiated from a 1/7-scale model main rotor of the AH-1 series helicopter. Averaged model scale data were compared with averaged full scale, inflight acoustic data under similar nondimensional test conditions. At low advance ratios (mu = 0.164 to 0.194), the data scale remarkable well in level and waveform shape, and also duplicate the directivity pattern of BVI impulsive noise. At moderate advance ratios (mu = 0.224 to 0.270), the scaling deteriorates, suggesting that the model scale rotor is not adequately simulating the full scale BVI noise; presently, no proved explanation of this discrepancy exists. Carefully performed parametric variations over a complete matrix of testing conditions have shown that all of the four governing nondimensional parameters - tip Mach number at hover, advance ratio, local inflow ratio, and thrust coefficient - are highly sensitive to BVI noise radiation.
Document ID
19850008517
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Splettstoesser, W. R.
(DFVLR Brunswick, United States)
Schultz, K. J.
(DFVLR Brunswick, United States)
Boxwell, D. A.
(NASA Ames Research Center Moffett Field, CA, United States)
Schmitz, F. H.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 5, 2013
Publication Date
December 1, 1984
Subject Category
Aerodynamics
Report/Patent Number
TM-84-A-7
AD-A159471
A-9854
NASA-TM-86007
NAS 1.15:86007
Accession Number
85N16826
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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