Effects of Pivot Location and Reduced Pitch Rate on Pitching Rectangular Flat Plates

This paper presents the results of an experimental investigation of the unsteady flow about pitching flat plates. Hydrodynamic force and two-dimensional particle image velocimetry measurements are reported for three pivot locations (leading edge, midchord, and trailing edge), reduced pitch rates from 0.022 to 0.39, and in still water, which corresponds to infinite reduced pitch rate. The wing has rectangular planform with effective aspect ratio 4, and the wing pitching motion is from 0 to 45 deg angle of attack. The relation between hydrodynamic force and vortical flow development as a function of pivot location and reduced pitch rate is discussed. Reasonable agreement is found between measured hydrodynamic force and quasi-steady potential flow theoretical results. Several vortical flow features are identified and discussed, including 1) the effect of pivot location and pitch acceleration on formation and evolution of vortical structures, 2) the impact of interaction between vortical flow structures on hy...