Role of the deviation motion on the aerodynamic performance of a mosquito wing in hover

The deviation angles during wing flapping motions are generally small for many insects and are known to have insignificant or even detrimental effects on the flight performance. Unlike many other insects, a mosquito hovers with a small sweeping amplitude but relatively large deviation angles. Thus, we investigate the effect of a deviation motion ('figure-eight' motion measured by Bomphrey et al. (2017)) on the aerodynamic performance of a mosquito wing in hover by comparing it with that without deviation motion (called in-plane motion). During the stroke, the deviation motion greatly changes the angle of attack and wing moving direction with respect to the stroke plane, but little changes the wing speed. These changes by the deviation motion significantly influence the instantaneous force and power generation. In particular, with the deviation motion, a large drag force is generated at early phase of the downstroke due to the increased angle of attack, and contributes to the vertical force generation. As results, the time-averaged vertical force is increased by the deviation motion, while the time-averaged power required is only slightly increased. Therefore, the mosquito wing generates a larger vertical force more efficiently with the deviation motion, suggesting that a deviation motion may be beneficial for an insect flight with a small sweeping amplitude.