蜻蜓非均匀柔性前翼扑动飞行的气动性能研究

为了探究柔性对于蜻蜓前翼在扑动向前飞行时的气动性能, 本文根据蜻蜓前翼的实际参数建立蜻蜓前翼模型, 提出了两种柔性分布方式即均匀柔性分布和沿蜻蜓前翼弦向的变柔性分布. 本文通过STAR-CCM+软件, 首先采用重叠网格和双向流固耦合技术, 用于实现蜻蜓前翼的扑动流固耦合, 其次通过改变蜻蜓前翼固体区域的杨氏模量函数从而实现蜻蜓前翼的两种不同柔性分布. 结果表明, 在均匀柔性分布条件下, 柔性翼在杨氏模量较小时的升力系数和阻力系数曲线的变化规律滞后于刚性翼半周期并且给飞行增加阻力, 但是随着杨氏模量的逐渐增加即柔性逐渐减小, 蜻蜓前翼受到的阻力减小, 获得的推力增加且推力给予蜻蜓前飞的动量增量、加速度以及时均推力系数先增加后减小. 在合理的非均匀柔性分布条件下, 柔性翼显著提高推力系数峰值和时均推力系数, 在扑动前飞时, 给予蜻蜓前翼较大的动量增量以及加速度. 两种柔性分布方式的蜻蜓前翼与刚性翼对比之下, 蜻蜓前翼在柔性为非均匀柔性分布时可以获得更好的气动性能. 

THE AERODYNAMIC PERFORMANCE OF NON-UNIFORM FLEXIBLE DRAGONFLY'S FOREWING IN FLAPPING FLIGHT1)

In order to explore the effect of flexibility on the aerodynamic performance of dragonfly forewing when flapping forward, this paper is established the forewing model according to the actual parameters of dragonfly, and put forward two flexible distribution modes along the chordwise, which are uniform flexibility distribution and variable flexibility distribution. Firstly, the overlapping grid and bidirectional fluid structure coupling technology are used to realize the fluid structure coupling of the dragonfly forewing in the flapping process by STAR-CCM+. Secondly, then the non-uniform flexible distribution of the forewing is realized by changing the young's modulus function in the solid region of the dragonfly forewing. According to the calculated results, it can be concluded that under the condition of uniform flexible distribution, only when the young's modulus is small, the change trend of the lift coefficient and drag coefficient curves of the flexible wing lags behind the half period of the rigid wing and further added more drag to the flight. However, with the gradual increase of Young's modulus, the drag of the dragonfly forewing decreases, the thrust increases, and the momentum increment, acceleration and time average thrust coefficient given by the thrust to the dragonfly forward flight first increase and then decrease. Under the condition of reasonable non-uniform flexible distribution, the flexible wing significantly improves the peak thrust coefficient and time average thrust coefficient. When flying forward, the dragonfly forewing is given a large momentum increment and acceleration. Compared with the rigid wing and the dragonfly forewing with two flexible distribution modes, the dragonfly forewing can obtain better aerodynamic performance when the flexibility is non-uniform flexible distribution.