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Advancing-side directivity and retreating-side interactions of model rotor blade-vortex interaction noiseAcoustic data are presented from a 40 percent scale model of the four-bladed BO-105 helicopter main rotor, tested in a large aerodynamic wind tunnel. Rotor blade-vortex interaction (BVI) noise data in the low-speed flight range were acquired using a traversing in-flow microphone array. Acoustic results presented are used to assess the acoustic far field of BVI noise, to map the directivity and temporal characteristics of BVI impulsive noise, and to show the existence of retreating-side BVI signals. The characterics of the acoustic radiation patterns, which can often be strongly focused, are found to be very dependent on rotor operating condition. The acoustic signals exhibit multiple blade-vortex interactions per blade with broad impulsive content at lower speeds, while at higher speeds, they exhibit fewer interactions per blade, with much sharper, higher amplitude acoustic signals. Moderate-amplitude BVI acoustic signals measured under the aft retreating quadrant of the rotor are shown to originate from the retreating side of the rotor.
Document ID
19880013326
Acquisition Source
Legacy CDMS
Document Type
Technical Publication (TP)
Authors
Martin, R. M. (NASA Langley Research Center Hampton, VA., United States)
Splettstoesser, W. R. (Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Brunswick (Germany, F.R.), United States)
Elliott, J. W. (NASA Langley Research Center Hampton, VA., United States)
Schultz, K.-J. (Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt Brunswick, Germany)
Date Acquired
September 5, 2013
Publication Date
May 1, 1988
Subject Category
Acoustics
Report/Patent Number
L-16354
NAS 1.60:2784
AVSCOM-TR-87-B-3
NASA-TP-2784
Accession Number
88N22710
Funding Number(s)
PROJECT: RTOP 505-61-51-06
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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