Pausing after clap reduces power required to fling wings apart at low Reynolds number
Pausing after clap reduces power required to fling wings apart at low Reynolds number
复制标题
拍手后暂停可降低在低雷诺数条件下机翼扇开所需的功率
DOI：
10.1088/1748-3190/ac050a
复制
发表时间：
2021-09-01
影响因子：
3.4
通讯作者：
Santhanakrishnan, Arvind
中科院分区：
文献类型：
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作者：
Kasoju, Vishwa T.;Santhanakrishnan, Arvind
最小的飞行昆虫，如蓟马（体长< 2 mm），面临的挑战是需要在10量级的基于弦的雷诺数（Re-c）下在空气中移动。在如此低的Re-c下，显著的粘性耗散需要相当大的能量消耗，以使微小的昆虫保持在高处。蓟马以大的行程幅度拍打它们浓密的刚毛翅膀，在上升行程结束时使两个翅膀彼此靠近（“拍手”），并在下降行程开始时将它们的翅膀分开（“投掷”）。从高速视频的自由起飞的蓟马，我们观察到，他们的前翅保持拍手约10%的wingbeat周期开始前的下冲程（fly中风）。我们试图检验在Re-c = 10时，在上冲程（拍动冲程）之后和下冲程（拍动冲程）之前暂停机翼运动是否有空气动力学上的好处。一个动态缩放的机器人拍手和投掷平台被用来测量产生的升力和阻力的物理模型的固体（非刚毛）和刚毛机翼在单翼和机翼对配置，暂停时间范围在0%至41%的周期。对于固体和刚毛翼对，暂停开始前的下降冲程（甩中风）消散涡产生的结束上升冲程（拍中风）。这导致下降的阻力系数平均下降整个下冲程（飞冲程），并反过来降低了功率要求。此外，与单翼布局相比，增加停顿时间会导致双翼布局的无量纲功率系数有较大的下降。我们的研究结果表明，翼翼相互作用中观察到的拍手和投掷运动的微小昆虫翅膀是必要的，以实现空气动力学的好处，在投掷前暂停，通过减少所需的功率拍手和投掷一个小的妥协，在电梯。
The smallest flying insects, such as thrips (body length < 2 mm), are challenged with needing to move in air at a chord-based Reynolds number (Re-c) of the order of 10. Pronounced viscous dissipation at such a low Re-c requires considerable energetic expenditure for tiny insects to stay aloft. Thrips flap their densely bristled wings at large stroke amplitudes, bringing both wings in close proximity to each other at the end of upstroke ('clap') and moving their wings apart at the start of downstroke ('fling'). From high-speed videos of free take-off flights of thrips, we observed that their forewings remain clapped for approximately 10% of the wingbeat cycle before the start of downstroke (fling stroke). We sought to examine if there are aerodynamic advantages associated with pausing wing motion after upstroke (clap stroke) and before downstroke (fling stroke) at Re-c = 10. A dynamically scaled robotic clap and fling platform was used to measure lift and drag forces generated by physical models of solid (non-bristled) and bristled wings in single wing and wing pair configurations, for pause times ranging between 0% to 41% of the cycle. For solid and bristled wing pairs, pausing before the start of downstroke (fling stroke) dissipated vorticity generated at the end of upstroke (clap stroke). This resulted in a decrease in the drag coefficient averaged across downstroke (fling stroke) and in turn reduced power requirements. Also, increasing the pause time resulted in a larger decrease in the dimensionless power coefficient for the wing-pair configurations compared to the single-wing configurations. Our findings show that wing-wing interaction observed in the clap and fling motion of tiny insect wings is necessary to realize the aerodynamic benefits of pausing before fling, by reducing the power required to clap and fling for a small compromise in lift.