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Helicopter main-rotor noise: Determination of source contributions using scaled model dataAcoustic data from a test of a 40 percent model MBB BO-105 helicopter main rotor are scaled to equivalent full-scale flyover cases. The test was conducted in the anechoic open test section of the German-Dutch Windtunnel (DNW). The measured data are in the form of acoustic pressure time histories and spectra from two out-of-flow microphones underneath and foward of the model. These are scaled to correspond to measurements made at locations 150 m below the flight path of a full-scale rotor. For the scaled data, a detailed analysis is given for the identification in the data of the noise contributions from different rotor noise sources. Key results include a component breakdown of the noise contributions, in terms of noise criteria calculations of a weighted sound pressure level (dBA) and perceived noise level (PNL), as functions of rotor advance ratio and descent angle. It is shown for the scaled rotor that, during descent, impulsive blade-vortex interaction (BVI) noise is the dominant contributor to the noise. In level flight and mild climb, broadband blade-turbulent wake interaction (BWI) noise is dominant due to the absence of BVI activity. At high climb angles, BWI is reduced and self-noise from blade boundary-layer turbulence becomes the most prominent.
Document ID
19880017523
Acquisition Source
Legacy CDMS
Document Type
Technical Publication (TP)
Authors
Brooks, Thomas F.
(Planning Research Corp. Hampton, VA., United States)
Jolly, J. Ralph, Jr.
(Planning Research Corp. Hampton, Va., United States)
Marcolini, Michael A.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
September 5, 2013
Publication Date
August 1, 1988
Subject Category
Acoustics
Report/Patent Number
NASA-TP-2825
L-16399
NAS 1.60:2825
Accession Number
88N26907
Funding Number(s)
PROJECT: RTOP 505-63-51
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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