Insects are excellent fliers because of their ability to generate precise wing kinematics and deform their wings for the sufficient production of unsteady aerodynamic forces. Most of the previous studies on the effects of wing kinematics on the aerodynamics have been limited to the use of rigid wings, and leaves the contribution of wing flexibility unknown. Here, an experiment was conducted to investigate the effect of varied sweep duration and timing of rotation on the unsteady aerodynamic characteristics of hovering flexible and rigid wings at Re of 10⁴. This study found that the forces generated by the flexible wing showed a conspicuous phase delay, which was more sensitive to the change in sweep duration than the timing of rotation. The transient negative lift associated with rigid wings undergoing delayed and advanced wing rotations totally disappeared in the flexible case. A digital particle image velocimetry (DPIV) measurement at the middle of stroke revealed a slight difference in the vortical structures surrounding the two wings in terms of proximity to the shed trailing-edge vortices (TEVs). Also, the linearly twisted nature of the flexible wing caused the coherent leading-edge vortex (LEV) to be stabilized throughout the wingspan. This increased the radial limit of the delayed stall from 3.6c in the rigid wing to 4.8c in the flexible wing. In general, the flexible wing with symmetric and delayed wing rotations generated the higher efficiency. The corresponding net force vectors were tilted in an almost vertical direction in comparison to the rigid wing. This is an indication that natural fliers adopt specific wing kinematics in addition to their wing deformation for the upward titling of their net force vector, which will significantly enhance their aerodynamic performance.

昆虫是优秀的飞行者，因为它们能够产生精确的机翼运动学并使其机翼变形以产生足够的不稳定空气动力。以前关于机翼运动学对空气动力学影响的大多数研究仅限于使用刚性机翼，而机翼柔韧性的贡献尚不清楚。在这里，进行了一项实验来研究不同的扫掠持续时间和旋转时间对悬停柔性和刚性机翼在Re为 10 ^{4 时}的非定常气动特性的影响。. 该研究发现，柔性机翼产生的力表现出明显的相位延迟，其对扫掠持续时间的变化比旋转时间更敏感。在柔性情况下，与经历延迟和提前机翼旋转的刚性机翼相关的瞬态负升力完全消失。在中风中间进行的数字粒子图像测速 (DPIV) 测量显示，在与棚后缘涡流 (TEV) 的接近度方面，两个机翼周围的涡流结构略有不同。此外，柔性机翼的线性扭曲特性导致连贯的前缘涡流 (LEV) 在整个翼展上保持稳定。这将延迟失速的径向限制从刚性机翼中的 3.6c 增加到柔性机翼中的 4.8c。一般来说，具有对称和延迟机翼旋转的灵活机翼产生了更高的效率。与刚性机翼相比，相应的净力矢量在几乎垂直的方向上倾斜。这表明，自然飞行者除了采用机翼变形外，还采用特定的机翼运动学来使其净力矢量向上倾斜，这将显着提高其空气动力学性能。