Blade‐Vortex Interaction Acoustic Results from a Forty Percent Model Rotor in the DNW
Abstract:Acoustic data from a 40 percent scale model of the 4‐bladed BO‐105 main rotor, measured in a large test section aeroacoustic wind tunnel, are presented. Rotor blade‐vortex interaction (BVI) noise data were acquired using a traversing in‐flow microphone array in the low to moderate speed flight range. Results are presented which document the flight conditions for maximum BVI impulsive noise; assess the acoustic farfield of BVI noise; map the directivity of BVI impulsive noise in a large plane below and upstream of the rotor; illustrate the temporal characteristics of the BVI signals as a function of advance ratio; and show the existence of retreating side BVI signals. The occurrence of a strongly focused radiation pattern, as opposed to a more omnidirectional pattern, was found to be very dependent on rotor operating condition. Multiple interactions per blade were observed at the lowest speed eases, with less sharp impulsive content, while the higher speed cases exhibited fewer interactions per blade, with much sharper, higher amplitude acoustic signals. BVI acoustic signals were measured under the aft retreating quadrant of the rotor and found to originate from the retreating side of the rotor.
Document Type: Research Article
Affiliations: NASA Langley Research Center, Hampton, Va.
Publication date: January 1, 1988
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