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Trailing Vortex Measurements in the Wake of a Hovering Rotor Blade with Various Tip ShapesThis work examined the wake aerodynamics of a single helicopter rotor blade with several tip shapes operating on a hover test stand. Velocity field measurements were conducted using three-component laser Doppler velocimetry (LDV). The objective of these measurements was to document the vortex velocity profiles and then extract the core properties, such as the core radius, peak swirl velocity, and axial velocity. The measured test cases covered a wide range of wake-ages and several tip shapes, including rectangular, tapered, swept, and a subwing tip. One of the primary differences shown by the change in tip shape was the wake geometry. The effect of blade taper reduced the initial peak swirl velocity by a significant fraction. It appears that this is accomplished by decreasing the vortex strength for a given blade loading. The subwing measurements showed that the interaction and merging of the subwing and primary vortices created a less coherent vortical structure. A source of vortex core instability is shown to be the ratio of the peak swirl velocity to the axial velocity deficit. The results show that if there is a turbulence producing region of the vortex structure, it will be outside of the core boundary. The LDV measurements were supported by laser light-sheet flow visualization. The results provide several benchmark test cases for future validation of theoretical vortex models, numerical free-wake models, and computational fluid dynamics results.
Document ID
Document Type
Preprint (Draft being sent to journal)
Martin, Preston B.
(NASA Ames Research Center Moffett Field, CA, United States)
Leishman, J. Gordon
(Maryland Univ. College Park, MD, United States)
Date Acquired
September 7, 2013
Publication Date
January 1, 2003
Subject Category
Fluid Mechanics And Thermodynamics
Meeting Information
Meeting: 58th AHS International Annual Forum
Location: Montreal
Country: Canada
Start Date: June 11, 2002
End Date: June 13, 2002
Sponsors: American Helicopter Society, Inc.
Distribution Limits
Public Use Permitted.
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