蜂蝇快速起飞过程的实验观测及力学分析

Experimental Measurement and Force Analysis of a Fast Takeoff in Dronefly

通过实验观测蜂蝇的快速起飞过程,并计算分析其中的力学过程。利用三维高速图像测量技术观测了整个过程中身体及翅膀的运动学参数,并且扫描记录了昆虫的形态学数据。采用所测得数据处理得到起飞过程中的惯性力和力矩,利用计算流体力学(CFD)方法计算翅膀拍动产生的气动力,由力学平衡得到腿部作用力。在快速起飞时经过2次完整拍动其拍动幅角增大到最大值,经过4次完整拍动之后拍动频率变为恒定,并且昆虫完全升入空中。离地之前主要由腿部作用力支撑体重及产生向上的加速度,同时在水平和俯仰转动方向消除气动力产生的不利影响,直到离地时腿部作用力变为零。表明蜂蝇具备通过增加腿部用力来达到快速起飞从而躲避天敌的能力,相比自主起飞缩短了起飞时间,也为人造微小型飞行器(MAV)的不同起飞模式的设计提供了思路。

An experimental measurement of a fast takeoff in dronefly is projected and the force analysis is presented here.Wing and body kinematics of the insect during takeoff are measured using high-speed video techniques and the morphological data are recorded.Based on the measured data,the inertia force acting on the insect is computed and the aerodynamic force of the wings is calculated by the method of computational fluid dynamics （CFD）.The leg force is determined according to force balance.In the takeoff,the stroke amplitude reaches a maximum value after two completed wingbeats,and after four wingbeats the wingbeat frequency stays constant and the insect is airborne.The leg force plays a primary role in the body raise movement and decreases the influence of aerodynamic force in horizontal and pitch motion,and decreases to zero when the insect is airborne.These indicate that droneflies get the ability to take off quickly to avoid predators using their legs,and the takeoff duration decreases compared with the voluntary takeoff.It is also an inspiration for the takeoff mode of man-made micro air vehicle （MAV）.