小型和超小型昆虫的扑翼模式变化
Flapping-pattern change in small and very small insects
摘要：
中型和大型昆虫在正常悬停水平，平面向上和向下冲程1 -4。由前缘涡产生的两个半冲程的升力提供了支撑重量的垂直力。但是，对于小型昆虫（翅长R小于约4 mm，雷诺数Re非常低，约80至10），由于空气粘性的大影响（当Re变得非常低时，在空气中运动就像在油中一样），如果使用上述翼运动学，则不能产生足够的垂直力。小昆虫必须使用不同的扑翼模式。本文通过对一种相对较大的小型昆虫（果蝇：R=3 mm，Re=80）和一种非常小的昆虫（黄蜂：R= 0.5mm，Re=10）的飞行数据分析，提出了一个关于扑翼模式如何变化的假设：随着昆虫大小或Re的减小，一个越来越深的U形上升冲程将用来克服粘性效应。我们通过测量不同大小物种的翅膀运动学来测试这一假设，以获得Re从80到10的数据，并通过计算气动力。实验数据和计算结果支持了我们的假设：平面上升冲程转变为U型上升冲程，上升冲程随尺寸或Re的减小而加深;对于相对较大的小昆虫，U形上升冲程通过具有较大的翼速度而产生比平面上升冲程更大的垂直力，并且对于非常小的昆虫，深U形上升冲程产生大的瞬时阻力，通过机翼的快速向下加速度几乎指向上方，提供所需的垂直力。
英文摘要：
Medium and large insects in normal hovering have horizontal, planar up- and downstrokes1-4. The lift of the two half-strokes, generated by the leading-edge vortex, provides the weight-supporting vertical force. But for small insects (wing length R less than about 4 mm and Reynolds number Re very low, about 80 to 10), because of the large effect of air viscosity (as Re becomes very low, moving in air is like in oil), sufficient vertical force could not be produced if using the above wing kinematics. Small insects must use different flapping mode. Here, through analyzing flight data from our recent studies on a relatively-large small insect (fruitfly: R=3 mm, Re=80) and a very small insect (wasp: R=0.5 mm, Re=10), we put forward a hypothesis on how the flapping pattern will change: as insect-size or Re decreasing, a deeper and deeper U-shape upstroke will be used to overcome the viscous effect. And we test this hypothesis by measuring the wing kinematics for species of different sizes to obtain data for Re ranging from 80 to 10 and by computing the aerodynamic forces. The data and computation support our hypothesis: the planar upstroke changes to U-shape upstroke which becomes deeper as size or Re becomes smaller; for relatively-large small insects, the U-shape upstroke produces a larger vertical force than a planar upstroke by having a larger wing velocity, and for very small insects, the deep U-shape upstroke produces a large transient drag that points almost upwards by fast downward acceleration of the wing, providing the required vertical force.
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