Usherwood James R
Structure and Motion Lab, The Royal Veterinary College, North Mymms, Hatfield, Herts, UK.
Bioinspir Biomim. 2009 Mar;4(1):015003. doi: 10.1088/1748-3182/4/1/015003. Epub 2009 Mar 4.
Predictions from aerodynamic theory often match biological observations very poorly. Many insects and several bird species habitually hover, frequently flying at low advance ratios. Taking helicopter-based aerodynamic theory, wings functioning predominantly for hovering, even for quite small insects, should operate at low angles of attack. However, insect wings operate at very high angles of attack during hovering; reduction in angle of attack should result in considerable energetic savings. Here, I consider the possibility that selection of kinematics is constrained from being aerodynamically optimal due to the inertial power requirements of flapping. Potential increases in aerodynamic efficiency with lower angles of attack during hovering may be outweighed by increases in inertial power due to the associated increases in flapping frequency. For simple hovering, traditional rotary-winged helicopter-like micro air vehicles would be more efficient than their flapping biomimetic counterparts. However, flapping may confer advantages in terms of top speed and manoeuvrability. If flapping-winged micro air vehicles are required to hover or loiter more efficiently, dragonflies and mayflies suggest biomimetic solutions.
空气动力学理论的预测结果往往与生物学观察结果相差甚远。许多昆虫和几种鸟类习惯于悬停，经常以低前进比飞行。根据基于直升机的空气动力学理论，即使对于非常小的昆虫，主要用于悬停的翅膀也应在低攻角下运行。然而，昆虫翅膀在悬停时以非常高的攻角运行；攻角的减小应该会带来可观的能量节省。在此，我考虑了一种可能性，即由于拍打所需的惯性功率，运动学的选择受到限制，无法达到空气动力学上的最优状态。在悬停时，随着攻角降低，空气动力学效率可能的提高，可能会被由于拍打频率相应增加而导致的惯性功率增加所抵消。对于简单的悬停，传统的旋翼式直升机类微型飞行器比拍打式仿生微型飞行器更高效。然而，拍打在最高速度和机动性方面可能具有优势。如果要求拍打式微型飞行器更高效地悬停或徘徊，蜻蜓和蜉蝣提供了仿生解决方案。
