Associate Scientist, Temasek Laboratories, National University of Singapore, Singapore, 117411, Singapore.
Bioinspir Biomim. 2019 Feb 27;14(3):036006. doi: 10.1088/1748-3190/ab0477.
The clap-and-fling effect, first observed in a number of insects, serves as a lift-enhancing mechanism for bio-inspired flapping wing micro aerial vehicles (MAV). In our comprehensive literature survey, we observe that the effect manifests differently in insects and contemporary MAVs; insects have active control over the angle of attack and stroke plane of the wing, whereas a number of kinematic parameters of an MAV's flexible wings are determined passively. Although there is consensus that flinging motion significantly enhances aerodynamic lift, the effect of clapping motion is not well-studied. To address this gap, we experimentally quantify the contribution of clapping motion using force measurement and particle image velocimetry. No significant enhancement in lift was observed due to clapping motion, because the momentum jet was too weak. However, the kinematics and flow conditions in our study were notably different from those in the previous studies on insect models. The wings of the MAV are flexible, and deform passively. Hence, the clapping of the trailing edges, and the appearance of a trailing edge momentum jet, was delayed and significantly suppressed. Using force measurement and CFD simulations, it was also found that the lesser the distance between the leading edges of the wings at the end of clap, the higher is the lift due to the subsequent fling.
拍打-甩动效应最初在许多昆虫中被观察到，它是一种用于仿生扑翼微型飞行器（MAV）的升力增强机制。在我们的全面文献调查中，我们观察到该效应在昆虫和现代 MAV 中表现不同；昆虫可以主动控制机翼的攻角和冲程平面，而 MAV 柔性机翼的许多运动学参数是被动确定的。尽管人们普遍认为甩动运动显著增强了空气动力学升力，但拍打运动的效果尚未得到很好的研究。为了解决这一差距，我们使用力测量和粒子图像测速法实验定量评估了拍打运动的贡献。由于动量射流太弱，拍打运动并没有显著提高升力。然而，我们的研究中的运动学和流场条件与之前对昆虫模型的研究明显不同。MAV 的机翼是柔性的，并且被动变形。因此，尾缘的拍打和尾缘动量射流的出现被延迟并显著抑制。通过力测量和 CFD 模拟，还发现拍打结束时机翼前缘之间的距离越小，由于随后的甩动，升力就越高。
