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Vortex Core Size in the Rotor Near-WakeUsing a kinetic energy conservation approach, a number of simple analytic expressions are derived for estimating the core size of tip vortices in the near-wake of rotors in hover and axial-flow flight. The influence of thrust, induced power losses, advance ratio, and vortex structure on rotor vortex core size is assessed. Experimental data from the literature is compared to the analytical results derived in this paper. In general, three conclusions can be drawn from the work in this paper. First, the greater the rotor thrust, t h e larger the vortex core size in the rotor near-wake. Second, the more efficient a rotor is with respect to induced power losses, the smaller the resulting vortex core size. Third, and lastly, vortex core size initially decreases for low axial-flow advance ratios, but for large advance ratios core size asymptotically increases to a nominal upper limit. Insights gained from this work should enable improved modeling of rotary-wing aerodynamics, as well as provide a framework for improved experimental investigations of rotor a n d advanced propeller wakes.
Document ID
20040082235
Acquisition Source
Ames Research Center
Document Type
Technical Memorandum (TM)
Authors
Young, Larry A.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 7, 2013
Publication Date
June 1, 2003
Subject Category
Aerodynamics
Report/Patent Number
A-03010293
NASA/TM-2003-212275
Report Number: A-03010293
Report Number: NASA/TM-2003-212275
Funding Number(s)
OTHER: 727-01-21
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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