Vortex Dynamics around Pitching Plates
FLORIDA STATE UNIV TALLAHASSEE DEPT OF MECHANICAL ENGINEERING
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Vortex dynamics of wakes generated by rectangular aspect-ratio 2 and 4 and two-dimensional pitching at plates in free stream are examined with direct numerical simulation and water tunnel experiments. Evolution of wake vortices comprised of tip, leading-edge and trailing-edge vortices is compared with force history for a range of pitch rates. The plate pivots about its leading edge with reduced frequency from pi8 to pi48, which corresponds to pitching over 1 to 6 chord lengths of travel. Computations have reasonable agreement with experiments, despite large differences in Reynolds number. Computations show that the tip effects are confined initially near the wing tips, but begin to strongly affect the leading-edge vortex as the motion of the plate proceeds, with concomitant effects on lift and drag history. Scaling relations based on reduced frequency are shown to collapse aerodynamic force history for the various pitch rates.
- Fluid Mechanics