为了解鸟类翅膀折叠运动的作用,对一个专利中的折叠扑翼机构进行了数学建模,外翼的折叠运动由非定常过程中的气动力、弹性恢复力矩和惯性力决定。利用风洞试验和数值模拟两种方式对该折叠扑翼模型进行了研究。数值模拟和风洞试验结果表明:相对于非折叠扑翼,折叠翼能够有效提高平均升力;在一定范围内增加内翼扑动频率可以提高折叠翼平均升力系数,但对折叠翼平均阻力系数影响甚微;一个扑动周期内折叠翼能量耗损小于非折叠翼;各力系数曲线揭示了折叠翼与非折叠翼气动特性差别的原因。所以,在扑翼飞行器设计时采用折叠运动是有利的。
Because of the potential use of micro air vehicles, the flapping wing mechanism has generated a great deal of interest. To understand the effect of the flexure of bird wings, a mathematical model of a patented flapping wing with a wing flexure is built and then investigated systematically by a wind tunnel experiment and numerical computation. In the computation the deflection angle of the outer wing is decided by the unsteady aerodynamic forces, the elastic moment and the inertia force. The experiment and computation results indicate that the wing flexure can increase the average lift of the flapping wing. Within a certain range, the larger the flapping frequency of the inner wing is, the greater the average lift coefficient will be. But the average drag coefficient is weakly dependent on the inner wing flapping frequency. The flapping wing with a wing flexure consumes less energy than that without a wing flexure in a flapping cycle. The force curves may account clearly for the differences of aerodynamics between a flapping wing with and without a wing flexure. Therefore it is very important to consider adopting a wing flexure in flapping wing design.
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