Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle between the crosswind and the flight direction varied from 0^o to 90^o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle on each dragonfly wing are different, e.g., has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

中文翻译：

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侧风中蜻蜓翅膀拍打气动性能的数值研究

通过三维非稳态Navier-Stokes方程的求解，进行了数值模拟，以研究侧风对刚性蜻蜓状扑翼的空气动力学特性的影响。当侧风与飞行方向之间的侧滑角从0 ^o变为90 ^o时，检查了四个蜻蜓翅膀的空气动力，力矩和流动结构。分析了蜻蜓模型在侧风中的稳定性。结果表明，侧滑角对总时间平均提升力影响不大，但对总时间平均推力，横向力和三向扭矩的影响却很大。侧滑角的增加会导致更大的总时间平均横向力和偏航力矩。这些可能会加速蜻蜓的横向偏斜，并且增加的滚动和俯仰力矩将进一步加剧蜻蜓模型的不稳定性。由于侧风的作用，机翼上的涡流和重新附着的气流横向移动到一侧，机翼表面的压力不再对称，因此，两侧机翼的空气动力之间的平衡被打破。侧滑角对每个蜻蜓翼的影响是不同的，例如，对后翼的空气动力的影响要比前翼的空气动力更大。当检测到侧风时，最好控制仿生蜻蜓状微型飞行器的两个后翼。