Helicopter Blade-Vortex Interaction Locations: Scale-Model Acoustics and Free-Wake Analysis Results.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CENTER
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The results of a model rotor acoustic test in the Langley 4- by 7-Meter Tunnel are used to evaluate a free-wake analytical technique. An acoustic triangulation technique is used to locate the position in the rotor disk where the blade-vortex interaction noise originates. These locations, along with results of the rotor free-wake analysis, are used to define the geometry of the blade-vortex interaction noise phenomena as well as to determine if the free-wake analysis is a capable diagnostic tool. Data from tests of two teetering rotor systems are used in these analyses. Keywords Helicopter rotor disks Free wake Blade-vortex interactions Acoustic properties.