Aerodynamic explanation of flight speed limits in hawkmoth-like flapping-wing insects
Aerodynamic explanation of flight speed limits in hawkmoth-like flapping-wing insects
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DOI：
10.1103/physrevfluids.7.093104
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发表时间：
2022-09-30
影响因子：
2.7
通讯作者：
Li, Chengyu
中科院分区：
文献类型：
--
作者：
Lionetti, Seth;Hedrick, Tyson L.;Li, Chengyu
天蛾能够在较低的速度下保持稳定的悬停或水平飞行。然而，以前的风洞实验表明，尽管飞行姿态发生了变化，但在较高的飞行速度（> 4.0 m/s）下，长序列的稳定向前飞行并不常见。这个飞行速度大约是基于其身体质量的理论预测的一半。目前还不清楚为什么没有观察到天蛾以更高的速度稳定飞行。本文的目的是比较涉及的空气动力学鹰蛾悬停那些在向前飞行。高速视频记录和三维表面重建被用来捕捉一个天蛾的翅膀运动学悬停时，并在向前飞行速度为2和4米/秒。在重建之后，使用基于内部浸没边界法的计算流体动力学（CFD）求解器来模拟昆虫模型。计算流体动力学解算器提供了持续飞行过程中产生的力、功率消耗和涡流结构的定量测量。这些结果使分析的某些趋势，如何天蛾调整扑动运动学及其相关的非定常空气动力学变化在不同的飞行速度。结果表明，蛾的阻力最小化，随着飞行速度的增加，但它立即失去了它的升力产生上升冲程，即使在缓慢的向前飞行速度（2米/秒）。在高向前飞行速度（4 m/s）的上升冲程期间产生大量的负升力。上升冲程中的这种负升力潜在地降低了最大持续飞行速度。这篇论文提供了对飞行昆虫低速飞行的物理学认识。
The hawkmoth is able to sustain a steady hover or level flight at lower speeds. However, previous wind tunnel experiments have suggested that long sequences of steady forward flight are less common at higher flying speeds (> 4.0 m/s) despite changes to the flight posture. This flying speed is about one-half of the theoretical prediction based on its body mass. It is unclear why hawkmoths have not been observed achieving steady flight at higher speeds. This paper aims to compare the aerodynamics involved in hawkmoth hovering to those in forward flight. High-speed video recordings and three-dimensional surface reconstruction were used to capture a hawkmoth's wing kinematics when hovering and at forward flight speeds of 2 and 4 m/s. Following reconstruction, the insect model was sim-ulated using an in-house immersed-boundary-method based computational fluid dynamics (CFD) solver. The CFD solver provided a quantitative measure of the force generation, power consumption, and vortex structures generated during sustained flight. These results enabled the analysis of certain trends in how a hawkmoth adjusts flapping kinematics and its associated unsteady aerodynamics changes across different flight speeds. The results show that the moth minimizes drag as flying speed increases, but it immediately loses its lift producing upstroke even at the slow forward flight speed (2 m/s). A significant amount of negative lift is generated during upstrokes at the high forward flying speed (4 m/s). This negative lift in the upstroke potentially reduces maximum sustained flight speeds. This paper provides physical insight into the low-speed flights in flying insects.