Laser Velocimetry Measurements of Oscillating Airfoil Dynamic Stall Flow Field
Abstract
Ensemble averaged two components velocity measurements over an airfoil experiencing
oscillatory dynamic stall under compressibility conditions were obtained. The
measurements show the formation of a separation bubble over the airfoil that persists
till angles of attack close to when the dynamic stall vortex forms and convects. The
fluid attains mean velocities as large as 1.6 times the free stream velocity (U(infinity))
with instantaneous values of 1.80 U(infinity). The airfoil motion induces these large velocities
in regions that are far removed from its surface. Also, depending upon the behavior
of the separation bubble, the wall jet profiles near the leading edge region could
become wake like over the airfoil in a cycle at different phase angles. Vorticity
contours indicate that the levels around the leading edge continuously increase till
the vortex begins to convect. Some of the measurements difficulties, especially,
particle behavior are discussed as well.
Description
AIAA Paper 91-1799, Jun. 1991, Honolulu, HI.
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