Department of Engineering Science and Ocean Engineering, National Taiwan University, 10617 Taipei, Taiwan.
Department of Mechanical Engineering, National Taiwan University, 10617 Taipei, Taiwan.
Phys Rev E. 2019 Dec;100(6-1):063102. doi: 10.1103/PhysRevE.100.063102.
In this work we studied the differences in flight kinematics and aerodynamics that could relate to differences in wing morphologies of a dragonfly and a damselfly. The damselflies and dragonflies normally fly with the fore wing or hind wing in the lead, respectively. The wing of the damselfly is petiolate, which means that the wing root is narrower than that of the dragonfly. The influence of the biological morphology between the damselfly and the dragonfly on their hovering strategies is worthy of clarification. The flight motions of damselflies and dragonflies in hovering were recorded with two high-speed cameras; we analyzed the differences between their hovering motions using computational fluid dynamics. The distinct mechanisms of the hovering flight of damselflies (Matrona cyanoptera) and dragonflies (Neurothemis ramburii) with different phase lags between fore and hind wings were deduced. The results of a comparison of the differences of wing phases in hovering showed that the rotational effect has an important role in the aerodynamics; the interactions between fore and hind wings greatly affect their vortex structure and flight performance. The wake of a damselfly sheds smoothly because of slender petiolation; a vertical force is generated steadily during the stage of wing translation. Damselflies hover with a longer translational phase and a larger flapping amplitude. In contrast, the root vortex of a dragonfly impedes the shedding of wake vortices in the upstroke, which results in the loss of a vertical force; the dragonfly hence hovers with a large amplitude of wing rotation. These species of Odonata insects developed varied hovering strategies to fit their distinct biological morphologies.
在这项工作中，我们研究了与蜻蜓和豆娘翅膀形态差异相关的飞行运动学和空气动力学差异。豆娘和蜻蜓通常分别以前翼或后翼领先飞行。豆娘的翅膀是有柄的，这意味着翅膀的根部比蜻蜓的要窄。豆娘和蜻蜓翅膀的生物学形态对它们悬停策略的影响值得澄清。我们使用两架高速摄像机记录了豆娘和蜻蜓的悬停飞行运动，并用计算流体动力学分析了它们悬停运动之间的差异。推导出了具有不同前翼和后翼相位滞后的豆娘（Matrona cyanoptera）和蜻蜓（Neurothemis ramburii）悬停飞行的不同机制。悬停时翅膀相位差异的比较结果表明，旋转效应在空气动力学中起着重要作用；前翼和后翼之间的相互作用极大地影响它们的涡结构和飞行性能。由于细长的柄状结构，豆娘的尾迹平稳地脱落；在翅膀平移阶段稳定地产生垂直力。豆娘悬停时的平移阶段较长，拍打幅度较大。相比之下，蜻蜓的根涡在向上冲程中阻碍了尾涡的脱落，导致垂直力的损失；因此，蜻蜓以较大的翅膀旋转幅度悬停。这些蜻蜓目昆虫发展了不同的悬停策略以适应其独特的生物学形态。
