蜂鸟在飞行过程中形成的不对称涡旋

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中：蜂鸟是多功能的自然飞行器，可以像昆虫一样进行运动，例如悬停，前进/后退飞行，转弯机动等。 不稳定的涡旋动力学是理解这些运动的空气动力学特征的关键。 在这里，我们提出了一种综合方法，结合高速摄影测量，机翼/体表跟踪和基于浸入边界方法的流动模拟来研究自由机动蜂鸟的三维涡动力学。 蜂鸟执行纯偏航转弯的模拟结果显示内翼和外翼之间的不对称尾流结构。 在下行程期间在外翼的近尾流中观察到双环涡旋结构，并且在上冲程期间观察到内环的结构。 机翼和这些复杂的涡旋结构之间的相互作用暗示了蜂鸟机动飞行中扑翼的空气动力学和动力学优势。

英：Hummingbirds are versatile natural flyers that can perform locomotion as insects, such as hovering, forward/backward flight, turning maneuver and more. The unsteady vortex dynamics is key to understand aerodynamic features of these motions. Here we present an integrated approach combining high-speed photogrammetry, wing/body surface tracking, and immersed boundary method based flow simulations to study the three-dimensional vortex dynamics of a freely maneuvering hummingbird. The simulation results of the hummingbird performing pure yaw turn show asymmetric wake structures between the inner and outer wings. Dual-loop vortex structures have been observed in the near wake of the outer wing during downstroke, and of the inner wing during upstroke. The interactions between the wings and these complex vortex structures have implied both aerodynamic and dynamic benefits of the flapping wings in hummingbird’s maneuvering flight.