The kinematics of insect flapping flight are complex and asymmetric, which are contributed to their superior flying capabilities, and the design of novel flapping micro air vehicles can draw inspiration from relevant researches. Previous studies usually focus on the wing with asymmetric stroke or pitch motions. A trajectory with asymmetric deviation motion, named as “pear-shaped” pattern, is proposed in current work. The hovering aerodynamics and vortex dynamics of a rigid flapping wing have been numerically investigated by comparing with that of “line-shaped” pattern with no deviation. In order to have a better insight into the influences of the asymmetric deviation, we change the kinematic parameters, that is, stroke amplitude, pitching amplitude, deviation amplitude, and phase lag between stroke and pitch angles. The results show that the wing with asymmetric deviation exhibits superior capability in lift enhancement for most of the cases analyzed, which is accompanied by the extra power cost and slight reduction in efficiency. The asymmetric deviation in cases with high stroke amplitude or low pitching amplitude may be considered as a cost-saving strategy, subject to slight damage on lift generation (if acceptable). Additionally, the asymmetric deviation brings a strong asymmetry into the instantaneous forces during one flapping cycle. The underlying lift-enhancing mechanism is explored by examining the dominant vortex structures in the adjacent flow field of the wing, which is mainly attributed to the changes in the effective angle of attack, increasing with downward deviation and decreasing with upward deviation.

昆虫扑翼飞行的运动学复杂且不对称，造就了其卓越的飞行能力，新型扑翼微型飞行器的设计可以从相关研究中汲取灵感。以前的研究通常集中在具有不对称行程或俯仰运动的机翼上。在当前工作中提出了一种具有不对称偏差运动的轨迹，称为“梨形”模式。通过与无偏差的“线形”模式的比较，对刚性扑翼的悬停空气动力学和涡流动力学进行了数值研究。为了更好地了解不对称偏差的影响，我们改变了运动学参数，即行程幅度、俯仰幅度、偏离幅度以及行程和俯仰角之间的相位滞后。结果表明，在所分析的大多数情况下，具有不对称偏差的机翼在升力增强方面表现出优异的能力，这伴随着额外的动力成本和效率的轻微降低。在具有高行程幅度或低俯仰幅度的情况下的不对称偏差可以被认为是一种节省成本的策略，但会对升力产生轻微损害（如果可以接受）。此外，不对称偏差在一个扑动循环期间给瞬时力带来了强烈的不对称性。通过检查机翼相邻流场中的主导涡结构来探索潜在的升力增强机制，其主要归因于有效攻角的变化，随着向下偏差增加，随着向上偏差减少。