Computational analysis of hydrodynamic interactions in a high-density fish school
Computational analysis of hydrodynamic interactions in a high-density fish school
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高密度鱼群水动力相互作用的计算分析
DOI：
10.1063/5.0028682
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发表时间：
2020-12-01
影响因子：
4.6
通讯作者：
Dong, Haibo
中科院分区：
文献类型：
--
作者：
Pan, Yu;Dong, Haibo
采用数值模拟的方法研究了高密度菱形鱼群中二维鱼形物体在波浪形横向运动下的水动力相互作用。本研究的重点是两个不同的流向间距，一个密集的学校与0.4的体长（BL）的间距和稀疏的学校与2.0 BL间距分别。基于浸没边界法的不可压缩Navier-Strokes流场求解器，然后定量模拟产生的流场模式和相关的推进性能的学校。结果表明，密集鱼群中的鱼获得更高的推力产生和更高的推进效率比在稀疏鱼群中，由于强大的墙壁效应，从邻近的鱼类。此外，在密集群中改变侧向间距的结果表明，随着侧向间距的减小，墙效应增强。流场分析表明，当横向间距小于0.6BL时，密集菱形鱼群中斜向游在领头鱼后面的鱼的尾流形态从2S转变为2 P。结果，在学校后面产生了一个有角度的射流，并为下游带来了更多的动量。同时，尾鱼的出现导致在领先鱼后面的更强的压力区域，并导致在密集鱼群中领先鱼的更高的水动力性能。这项研究揭示的见解将有助于了解鱼群的物理机制，并为生物启发的水下群体机器人提供新的游泳策略。
Numerical simulations are employed to study hydrodynamic interactions between two-dimensional fish-like bodies under a traveling wavy lateral motion in high-density diamond-shaped fish schools. This study focuses on two different streamwise spacings, a dense school with 0.4 body length (BL) spacing and a sparse school with 2.0 BL spacing, respectively. An immersed-boundary-method-based incompressible Navier-Strokes flow solver is then employed to quantitatively simulate the resulting flow patterns and associated propulsive performance of the schools. The results suggest that a fish in the dense school achieves higher thrust production and higher propulsive efficiency than that in the sparse school due to a strong wall effect from neighboring fishes. In addition, results from changing the lateral spacing in the dense school have shown that the wall effect is enhanced as the lateral spacing decreases. Flow analyses have shown that the wake pattern of the fish swimming diagonally behind the leading fish in a dense diamond-shaped school transfers from 2S to 2P when the lateral spacing is smaller than 0.6 BL. As a result, an angled jet is produced behind the school and brings more momentum downstream. At the same time, the appearance of the trailing fish results in a stronger pressure region behind the leading fish and leads to a higher hydrodynamic performance of the leading fish in the dense school. The insights revealed from this study will contribute to understanding physical mechanisms in fish schools and providing a new swimming strategy for bio-inspired underwater swarm robots.