Effect of stroke variations on the aerodynamic characteristics of a hovering wing

The wing kinematics of hovering insects are dominated by the stroke (back and forth motion of the wing) and pitch (change in angle-of-attack). The manipulation of these motions is known to impart superior aerodynamic qualities to biological fliers. The wing kinematics are complicated and difficult to replicate in human-engineered aerial vehicles. Popular approximations that are used to mimic the flapping wing stroke kinematics are sinusoidal, trapezoidal, and linear profiles. The influence of different stroke kinematics on the aerodynamic characteristics of a hovering wing is experimentally investigated in this study. The time-varying aerodynamic forces acting on the hovering wing are measured using a dynamically scaled mechanical model in a quiescent flow in the insect flight regime. Phase-locked flow field measurements are carried out at the mid span of a wing with an aspect ratio of 3. The dynamically relevant flow features are identified and tracked. The results are correlated with the aerodynamic forces to explain the effect of stroke variations during hover.