Experiments were conducted to examine the effect of sweep motion profile on the aerodynamic characteristics of flexible and rigid flapping wings in hover. The sweep motion was varied from triangular to sinusoidal profiles. The study revealed that the flexible wing was more sensitive to the change in motion profile by inducing a certain amount of phase delay. The sinusoidal and triangular profiles were found to be the most effective and efficient wing motions, respectively, for both wings. The presence of wing deformation increased the net force angle and led to a superior aerodynamic performance than the rigid wing. The flow visualization also revealed that the fully developed wake from the flexible wing motion was rather beneficial to augment the lift. This was contrary to the detrimental effect observed for the rigid wing. The wake increased the effective angle of attack, and subsequently augmented the lift in comparison with a quiescent flow. However, the overall wake was massively mitigated with stronger root vortex when the flexible wing was pitched at 45°. This implies that the insect wing deformation coupled with the surrounded wake effect during hovering flight might play a significant role in enhancing the lift.
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