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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, in-flight acoustic data under similar non-dimensional test conditions using an improved data analysis technique. At low advance ratios (mu = 0.164 - 0.194), the BVI impulsive noise data scale remarkably well in level, waveform, and directivity patterns. At moderate advance ratios (mu = 0.224 - 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. Measured BVI noise radiation is highly sensitive to all of the four governing nondimensional parameters--hover tip Mach number, advance ratio, local inflow ratio, and thrust coefficient.
Document ID
19990111581
Acquisition Source
Ames Research Center
Document Type
Reprint (Version printed in journal)
Authors
Boxwell, D. A.
(Army Aviation Research and Technology Activity Hampton, VA United States)
Schmitz, F. H.
(Army Aviation Research and Technology Activity Hampton, VA United States)
Splettstoesser, W. R.
(Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Brunswick, Germany)
Schultz, K. J.
(Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Brunswick, Germany)
Date Acquired
August 19, 2013
Publication Date
January 1, 1987
Publication Information
Publication: Journal of the American Helicopter Society
Publisher: American Helicopter Society
Volume: 32
Issue: 1
Subject Category
Aerodynamics
Distribution Limits
Public
Copyright
Other

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