单自由度扑翼模型脱落涡及其升力机制的实验研究

采用色流实验与particle image velocimetry(PIV)测量相结合的方法,对单自由度扑翼模型所产生的脱落涡进行实验研究,得到以下结论:①在扑翼上扑或下扑的过程中,前后缘处产生连续的牛角形涡环,且脱落涡均存在展向运动.②翼翅表面脱落涡的交替产生,使得翼翅上下表面交替产生不对称分布的压力差.③研究对象产生升力的条件是攻角与来流速度均不为零.④扑翼上扑和下扑过程中,脱落涡环量最大值均出现在单行程的3/5处.⑤脱落涡环量与扑动速度成正比.⑥相比上扑过程,下扑过程中翼翅对流场做功更多,在一个扑动周期内,这多余的能量转换为扑翼升力.

Experimental investigation on shedding vortex and lift mechanism of flapping wing model with single degree of freedom

Based on flow visualization experiment and particle image velocimetry (PIV) measurement, the shedding vortex of flapping wing model with single degree of freedom was studied experimentally and several conclusions were obtained as follow. (1) A horn-shape shedding vortex with a wingspan-direction movement is generated around the leading edge as well as the trailing edge during flapping. (2) The shedding vortex leads to alternative pressure differences with unequal scalar on both sides of the flapping wing. (3) Both attack angle and inflow speed are not zero, which are essential factors to the lift generation of study object. (4) The maximum circulation of the shedding vortex appears at about 3/5 of the upward flapping journey, as well as the downward flapping journey. (5) The circulation of the shedding vortex is proportional to the flapping speed. (6) The flapping wing generates more work during the downward flapping journey, as compared with the upward flapping journey, resulting in the generation of lift within a whole flapping cycle.