Collective behavior and hydrodynamic advantage of side-by-side self-propelled flapping foils.
Collective behavior and hydrodynamic advantage of side-by-side self-propelled flapping foils.
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DOI：
10.1103/physreve.105.065105
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发表时间：
2022-06
期刊：
影响因子：
--
通讯作者：
Xuechao Liu;Kui Liu;Haibo Huang
中科院分区：
文献类型：
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作者：
Xuechao Liu;Kui Liu;Haibo Huang
鱼群及其潜在的水动力优势是一个有趣的问题，由于系统的复杂性，特别是大型鱼群，许多潜在的机制尚不清楚。在这里，大型学校包含四个，六个，和八个自推进翼并排配置的数值研究。研究了两个相邻箔片之间的异相和同相的不同组合的影响。结果表明，在同步谐波扑翼运动的驱动下，多个平行自航翼可以自发形成稳定的并排构型。当与单独的单个翼片挥舞相比时，对于任何两个相邻翼片处于异相状态的情况，翼片以特定的巡航速度消耗更多的能量。对于任何两个相邻翼片处于同相状态的情况，翼片对于特定的扑动频率以较低的速度推进。有趣的是，处于异相和同相共存的混合状态的箔优选地用于提高速度和节省功率。进一步的分析表明，任意三个相邻翼片在混合状态下形成的同步协同尾涡结构和弓形构型是该构型稳定性和较低运输成本的主要原因。在一个扑动周期中，尾流中的协同涡帮助翼片交替向前运动。弓形结构可防止尾流横向扩散，提高性能。我们的论文揭示了一些光理解的自组织集体行为和大型学校的水动力优势。
Fish schools and their potential hydrodynamic advantages are intriguing problems and many underlying mechanisms are unclear due to the complexity of the system, especially for large schools. Here large schools containing four, six, and eight self-propelled foils in a side-by-side configuration are numerically studied. The effect of different combinations out of phase and in phase between two neighboring foils is studied. The results show that the multiple abreast self-propelled foils driven by synchronized harmonic flapping motions can spontaneously form stable side-by-side configurations. When compared with a single foil flapping alone, for cases in which any two neighboring foils are in an out-of-phase state, foils consume more energy with a specific cruising speed. For cases where any two neighboring foils are in an in-phase state, foils propel at a lower speed for a specific flapping frequency. Interestingly, the foils in hybrid states in which both out of phase and in phase coexist are preferred to enhance speed and save power. Further analysis indicates that the stability of the configuration and the lower cost of transport are attributed to the synchronized collaborative wake vortex structure and bow configuration formed by any three neighboring foils in a hybrid state. The collaborative vortices in the wake help the foils move forward alternatively during one flapping cycle. The bow configuration prevents the wake from spreading laterally and enhances the performance. Our paper sheds some light on understanding the self-organized collective behavior and hydrodynamic advantages of large schools.