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Experimental investigation of the flowfield of an oscillating airfoilThe flowfield of an airfoil oscillated periodically over a wide range of reduced frequencies, 0 less than or = k less than or = 1.6 is studied experimentally at chord Reynolds numbers of R sub c = 22,000 and 44,000. The NACA0012 airfoil is pitched sinusoidally about one quarter chord between angles of attack (alpha) of 5 and 25 degrees. Detailed flow visualization and phase averaged vorticity measurements are carried out for k = 0.2 to document the evolution and the shedding of the dynamic stall vortex (DSV). In addition to the DSV, an intense vortex of opposite sign originates from the trailing edge just when the DSV is shed. After being shed into the wake, the two together take the shape of a large 'mushroom' while being convected away from the airfoil. The unsteady circulation around the airfoil and, therefore, the time varying component of the lift is estimated in a novel way from the shed vorticity flux and is found to be in good agreement with the lift variation reported by others. The delay in the shedding of the DSV with increasing k, as observed by previous researchers, is documented for the full range of k. The DSV, for example, is shed nearly at the maximum alpha of 25 degrees at k = 0.2, but is shed at the minimum alpha of 5 degrees at k = 0.8. At low k, the flowfield appears quasi-steady and the bluff body shedding corresponding to the maximum alpha (25 degrees) dominates the unsteady fluctuations in the wake.
Document ID
19920020939
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Panda, J.
(NASA Lewis Research Center Cleveland, OH, United States)
Zaman, K. B. M. Q.
(NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1992
Subject Category
Aerodynamics
Report/Patent Number
AIAA PAPER 92-2622-CP
NAS 1.15:105675
E-7046
NASA-TM-105675
Meeting Information
Meeting: Applied Aerodynamics Conference
Location: Palo Alto, CA
Country: United States
Start Date: June 22, 1992
End Date: June 24, 1992
Sponsors: AIAA
Accession Number
92N30182
Funding Number(s)
PROJECT: RTOP 505-62-52
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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