Effect of aspect ratio and leading and trailing edge form on the flow around an impulsively pitching flat plate

In order to understand the three-dimensionality effects, i.e., the effect of experimental conditions to simulate a 3D unsteady flow around a finite wing, the flow fields in the near wake of a flat plate undergoing a pitch up motion has been investigated using a 2D2C Digital Particle Image Velocimetry (DPIV) system in conjunction with simultaneous force measurements. The experiments are performed in a large-scale free-surface water channel. An endplate used to prevent the free-surface effects represents the symmetry plane for the wing. To obtain the same aspect ratios without using the endplate, different but appropriately sized wings have been also used in a fully submerged arrangement. The wing, with either sharp or round, leading and trailing edges, has an aspect ratio ranging from 2 to 8, and pitches up to 45° in 1 or 6 convective time. The preliminary force measurement results reveal that the major differences occur after the motion is completed where the lift and drag forces show a local increase and decrease.