昆虫拍翼方式的非定常流动物理再探讨

UNSTEADY FLOW MECHANISMS REVISITED IN INSECT FLAPPING FLIGHT

基于提出的理论模化方法来探讨昆虫拍翼方式的非定常流动物理,以悬停飞行为例,通过对拍翼运动的分析,不仅解释了昆虫利用高频拍翼的方式为何能够克服低雷诺数带来的气动局限性(St》1/Re),而且还指出高升力产生和调节的3个流动控制因素: (1)由于拍翼的变速运动即时引起了流体动力响应,这种附加惯性效应可产生瞬时的高升力;(2)保持前缘涡不脱离翼面有助于减少升力的下降;(3)增大后缘涡的强度并加速其脱离后缘能够有效地提高升力.

The unsteady flow mechanisms of insect flapping flight are revisited with the theoretical modeling approach proposed. According to analysis of the flapping motion in insect hovering flight, it is revealed that, limitations of the aerodynamic lift at low Reynolds numbers may be released by the highly unsteady condition in insect wing flapping, in which case the controlling parameter is the Strouhal number (St>>1/Re). Furthermore, in the present theoretical modeling study, three factors have been found in lift generation and regulation: (1) the remarkable instantaneous added inertial effect is excited by the high unsteadiness of wing flapping; (2) keeping the leading edge vortex on the upper wing surface can avoid lift decreasing; (3) enhancing the strength of the trailing edge vortex and accelerating its shedding can produce high lift.