Flapping dynamics of an inverted flag behind a cylinder
Flapping dynamics of an inverted flag behind a cylinder
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圆柱体后面的倒旗的扑动动力学
DOI：
10.1088/1748-3190/ac96b9
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发表时间：
2022
影响因子：
3.4
通讯作者：
Shoele, Kourosh
中科院分区：
文献类型：
--
作者：
Ojo, Oluwafemi;Kohtanen, Eetu;Jiang, Aojia;Brody, Jacob;Erturk, Alper;Shoele, Kourosh
倒旗结构的灵感来自于生物结构（如树枝上的叶子），在较低流速下比常规旗结构表现出丰富的动态不稳定性。在生物对等体中，叶子和树枝在叶子上的排列创造了一个复杂的相互作用环境，促进了某些动态的飘动模式。虽然在降低流速时实现大振幅响应在能量收集等新兴领域是有利的，但人们对这种相互作用的后果知之甚少。在这项工作中，我们在数值上研究了典型的生物启发问题，即圆柱形钝体后面的二维倒旗的流动-结构相互作用，模拟树枝后面的叶子，以研究其独特的飘扬状态。逐步修正圆柱与旗杆的分离距离，确定不同流速下小幅或大幅扑动的有效距离。结果表明，当圆柱体放置在旗子前面足够大的距离时，旗子表现出周期性的大振幅-低频响应模式。在较小的距离上，当旗子在圆柱的直接尾迹内时，旗子经历高频-小幅度响应。最后，对不同几何参数和电学参数下旗子的压电能量收集能力进行了数值和实验研究。还确定了具有最高能量输出的两种独立的最优响应模式。
The inverted flag configuration is inspired by biological structures (eg leaves on a tree branch), showing rich dynamics associated with instabilities at lower flow speeds than the regular flag configuration. In the biological counterpart, the arrangement of leaves and twigs on foliage creates a complex interacting environment that promotes certain dynamic fluttering modes. While enabling a large amplitude response for reduced flow speeds is advantageous in emerging fields such as energy harvesting, still, little is known about the consequence of such interactions. In this work, we numerically study the canonical bio-inspired problem of the flow-structural interaction of a 2D inverted flag behind a cylindrical bluff body, mimicking a leaf behind a tree branch, to investigate its distinct fluttering regimes. The separation distance between the cylinder and flag is gradually modified to determine the effective distance beyond which small-amplitude or large-amplitude flapping occurs for different flow velocities. It is shown that the flag exhibits a periodic large amplitude− low frequency response mode when the cylinder is placed at a sufficiently large distance in front of the flag. At smaller distances, when the flag is within the immediate wake of the cylinder, the flag undergoes a high frequency− small amplitude response. Finally, the flag's piezoelectric power harvesting capability is investigated numerically and experimentally for varying geometrical and electrical parameters associated with these two conditions. Two separate optimal response modes with the highest energy output have also been identified.