On the competition between leading-edge and tip-vortex growth for a pitching plate
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The interaction between leading-edge-vortex and tip-vortex development on a low-aspect-ratio plate has been investigated and compared to a nominally two-dimensional rectangular flat plate. Simultaneous to force measurements, three-dimensional particle tracking velocimetry (3D-PTV) was used to characterize the instantaneous flow field on the suction side. An integration of the spanwise circulation distribution for the two-dimensional case indicates that the leading-edge-vortex formation process is correlated with the convective time and not with the instantaneous pitch angle. However, for the finite plate, it is found that the tip-vortex formation process is correlated with the instantaneous pitch angle instead. Since leading-edge vorticity is convected inboard by tip-vortex-induced spanwise velocity, leading-edge-vortex growth is found to be retarded in the tip region. Finally, with the aid of Lagrangian particle tracks, the leading-edge and tip vortices are found to grow distinct from one another, that is, no leading-edge vorticity is drawn into the tip vortex. However, the tip vortex is found to influence the leading-edge-vortex dynamics through inboard transport of leading-edge vorticity and is therefore responsible for vortex compression at the mid-span.
KeywordsVortex Lift Coefficient Spanwise Velocity Lagrangian Particle Track Arched Shape
The authors acknowledge the funding provided by the Natural Science and Engineering Research Council of Canada. The authors would also like to thank the constructive feedback from all three reviewers.
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