Fluid Dynamics of Pitching and Plunging Flat Plate at Intermediate Reynolds Numbers

A combined numerical and experimental study of two- and three-dimensional pitching and plunging flat plates at. Reynolds numbers of O(10(4)) is presented. The focus of this paper is the interplay between the geometry, kinematics, Reynolds numbers, and three-dimensional effects with the resulting aerodynamic forces and flow structures. A shallow-stall and a deep-stall motion with higher maximum effective angles of attacks are considered. Under both kinematic motions, massive leading-edge separation is observed at the sharp leading edge of the flat plate. This geometric effect is seen to dominate over other viscosity effects, and the Reynolds number dependence is limited. Compared with the blunter SD7003 airfoil, where the flow is mostly attached for the shallow-stall motion at Re = 6 x 10(4), the sharper leading edge of the flat plate leads to earlier and stronger leading-edge vortex formation and greater lift and drag. Finally, the presence of a tip vortex significantly reduces lift generation during the downstroke of an aspect ratio 2 flat plate undergoing the shallow-stall motion. During the upstroke, the tip vortex is weaker and the force on the aspect ratio 2 wing can be approximated by its two-dimensional counterpart.