Effects of Wing Morphology and Kinematics on Vortex Dynamics in Flapping Flight

The performance of flapping wings is closely associated with both wing morphology and kinematics. In this paper, we experimentally study the effects of aspect ratio and velocity profile of unsteady rotating plates on the resulting vortex dynamics. It is found that the size of the leading edge vortex (LEV) almost linearly increases along the wing span and the vortex structure is dominated by the dimensionless distance from the rotation center. The structure of the LEV is insensitive to the Reynolds number (Re) in our current Re range. Results of kinematics effect show that a gentle acceleration can keep the vortex structure more coherent during the rotation than an impulsive acceleration. However, the circulation is closely related to the real time velocity of the wing with a delay in response.