Actively bending flapping wings characterization

This study experimentally characterizes the flow generated by an actively deforming flapping wing. Active deformation is achieved using embedded piezoelectric actuators, which enable precise control of the wing bending. By phase-shifting the input electrical signal with respect to the flapping motion, the resulting bending motion is likewise phase-shifted relative to the flapping kinematics, allowing the influence of the bending phase lag, δθ , on the flow structures (and thus on the aerodynamic performance) to be characterized. This work focuses on two bending phase lags. In both cases, the wing reaches its maximum bending at stroke reversal. The first case corresponds to bending in the flapping direction (i.e. reduced effective flapping amplitude), whereas the second corresponds to bending in the opposite flapping direction (i.e. increased effective flapping amplitude). A scanning PIV technique is then employed to obtain volumetric velocity fields. The results show that the morphing wing with the first phase-lag generates less intense vortical structures than the morphing wing with the second phase-shift, suggesting that active control of the flapping-wing shape could be used to tailor the instantaneous aerodynamic loads.