Locomotion of a bioinspired flyer powered by one pair of pitching foils
Locomotion of a bioinspired flyer powered by one pair of pitching foils
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由一对投掷翼片驱动的仿生飞行器的运动
DOI：
10.1103/physrevfluids.3.013102
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发表时间：
2018
影响因子：
2.7
通讯作者：
Zhang Xing
中科院分区：
文献类型：
--
作者：
Zhang Xiang;He Guowei;Wang Shizhao;Zhang Xing
我们用数值方法研究了最近由Ristroph和奇尔德里斯[L.Ristroph和S.奇尔德里斯，J.R.Soc.接口11,20130992(2014年)]。这个简化的模型由两个刚性薄片组成，它们被强迫以反相方式倾斜。在模拟中，流体的Navier-Stokes方程和飞片的动力学方程被一起求解。我们首先考虑了飞行器模型只允许在垂直方向上运动的约束飞行条件。研究了控制参数对悬停性能的影响。根据参数值的变化，识别出三种不同的运动状态，即上升、下降和近似悬停。探讨了这三种运动状态对应的尾迹结构。经过长时间的模拟发现，由于尾迹对称性破缺的发生，近似悬停状态不再持续。然后我们考虑自由飞行的条件，其中允许三个自由度的运动。研究了重心位于几何中心的飞行器的姿态稳定性。研究了飞行器在不同运动状态下对物理和数值摄动的响应。我们的结果表明，微扰后的升态是可以恢复的。在摄动后，下降状态是不可恢复的，出现了类似于下降卡片的混合颤振和翻滚运动。近似的悬停状态也是不可恢复的，在摄动后最终转变为上升状态。研究结果对水母类飞行器的升力产生机理和稳定性有了一定的认识，有助于指导水母类飞行器的设计和优化。
We numerically investigate the flight dynamics and aerodynamics of a two-dimensional model for the jellyfishlike ornithopter recently devised by Ristroph and Childress [L. Ristroph and S. Childress, J. R. Soc. Interface 11, 20130992 (2014)]. This simplified model is composed of two rigid thin foils which are forced to pitch in antiphase fashion. The Navier-Stokes equations for the fluid and the dynamics equations for the flyer are solved together in the simulations. We first consider the constrained-flying condition where the flyer model is only allowed to move in the vertical direction. The influences of the control parameters on the hovering performance are studied. With the variations in parameter values, three different locomotion states, i.e., ascending, descending, and approximate hovering, are identified. The wake structures corresponding to these three locomotion states are explored. It is found that the approximate hovering state cannot persist due to the occurrence of wake symmetry breaking after long-time simulation. We then consider the free-flying condition where the motions in three degrees of freedom are allowed. We study the postural stability of a flyer, with its center of gravity located at the geometric center. The responses of the flyer at different locomotion states to physical and numerical perturbations are examined. Our results show that the ascending state is recoverable after the perturbation. The descending state is irrecoverable after the perturbation and a mixed fluttering and tumbling motion which resembles that of a falling card emerges. The approximate hovering state is also irrecoverable and it eventually transits to the ascending state after the perturbation. The research sheds light on the lift-producing mechanism and stability of the flyer and the results are helpful in guiding the design and optimization of the jellyfishlike flying machine.