展向柔性对扑翼推力影响原因的数值分析

THE NUMERICAL ANALYSIS OF THE REASON FOR THE EFFECT OF SPANWISE FLEXIBILITY ON FLAPPING WING THRUST

为研究展向柔性对扑翼推力的影响及产生影响的原因,该文使用一种折叠翼模型作为研究对象,改变展向折叠的弹性系数,联立求解N-S方程和刚体运动方程,并进行了展向柔性对推力影响原因的分析。结果表明:适当的展向柔性可以减小阻力系数,但过大的展向柔性却会增加阻力系数;展向柔性之所以能够改变阻力系数,是因为展向柔性的引入改变了有效攻角沿展向的分布。若展向柔性的引入能够增加有效攻角绝对值沿展向的分布,那么就可以减小瞬时阻力系数。

To investigate the effect of spanwise flexibility on a flapping thrust and the reason for the effect, a flapping wing model with spanwise wing flexure is selected. Both Navier-Stokes equations and rigid motion equations are solved with respect to different spanwise elastic constants. The results indicate that a degree of spanwise flexibility is found to yield a decrease in the drag coefficient. But introducing a far greater degree of spanwise flexibility is found to be detrimental. The reason for the effect of spanwise flexibility on drag coefficients is that introducing spanwise flexibility changes the distribution of effective angles along the spanwise direction. If introducing spanwise flexibility could increase the absolute magnitude of an effective angle along the span, then the instantaneous drag coefficient can be decreased.