Aerodynamic characteristics of flapping motion in hover

The aim of the present work is to understand the aerodynamic phenomena and the vortex topology of an unsteady flapping motion by means of numerical and experimental methods. Instead of the use of real insect/bird wing geometries and kinematics which are highly complex and difficult to imitate by an exact modeling, a simplified model is used in order to understand the unsteady aerodynamics and vortex formation mechanisms during the different phases of the flapping motion. The flow is assumed to be laminar with a Reynolds number of 1,000. Direct numerical simulations, laser sheet visualizations and particle image velocimetry (PIV) measurements are performed for the phenomenological analysis of the flow. The vortex dynamics and their identification are put in evidence with PIV measurements by considering velocity magnitude, streamlines, second invariant of velocity gradient (Q-criteria), vorticity contours and Eurlerian accelerations.