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BVI impulsive noise reduction by higher harmonic pitch control - Results of a scaled model rotor experiment in the DNWResults are presented of a model rotor acoustics test performed to examine the benefit of higher harmonic control (HHC) of blade pitch to reduce blade-vortex interaction (BVI) impulsive noise. A dynamically scaled, four-bladed, rigid rotor model, a 40-percent replica of the B0-105 main rotor, was tested in the German Dutch Wind Tunnel. Noise characteristics and noise directivity patterns as well as vibratory loads were measured and used to demonstrate the changes when different HHC schedules were applied. Dramatic changes of the acoustic signatures and the noise radiation directivity with the HHC phase variations are found. Compared to the baseline conditions (without HHC), significant mid-frequency noise reductions of locally 6 dB are obtained for low-speed descent conditions where GVI is most intense. For other rotor operating conditions with less intense BVI there is less or no benefit from the use of HHC. LF noise and vibratory loads, especially at optimum noise reduction control settings, are found to increase.
Document ID
19920073720
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Splettstoesser, Wolf R.
(NASA Langley Research Center Hampton, VA, United States)
Schultz, KLAUS-J.
(NASA Langley Research Center Hampton, VA, United States)
Kube, Roland
(DLR Braunschweig, Germany)
Brooks, Thomas F.
(NASA Langley Research Center Hampton, VA, United States)
Booth, Earl R., Jr.
(NASA Langley Research Center Hampton, VA, United States)
Niesl, Georg
(MBB GmbH Ottobrunn, Germany)
Streby, Olivier
(Aerospatiale Marignane, France)
Date Acquired
August 15, 2013
Publication Date
September 1, 1991
Subject Category
Acoustics
Accession Number
92A56344
Distribution Limits
Public
Copyright
Other

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