Lattices of Hydrodynamically Interacting Flapping Swimmers
Lattices of Hydrodynamically Interacting Flapping Swimmers
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DOI：
10.1103/physrevx.9.041024
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发表时间：
2019-11-01
影响因子：
12.5
通讯作者：
Shelley, Michael J.
中科院分区：
文献类型：
--
作者：
Oza, Anand U.;Ristroph, Leif;Shelley, Michael J.
鱼群和鸟群展现出复杂的集体动力学，其自组织原理在很大程度上尚不明确。从理论上讲，流体动力学对这类群体的影响相对尚未得到充分探索，部分原因是对许多动态物体之间长时间存在的流体动力相互作用进行建模存在困难。我们通过一种新颖的离散时间动力系统（迭代映射）来解决这个问题，该系统描述了排列成一维和二维晶格形式的拍动泳者之间的流体动力相互作用。我们的一维结果与先前发表的实验数据非常吻合，尤其预测了群聚状态的双稳态以及可在实验环境中探究的新的不稳定性。对于二维晶格，我们确定了泳者能从流体动力相互作用中获得最佳益处的队形。因此我们得到以下层级关系：虽然并排的单行“方阵”队形比单个泳者稍有改进，但一维直线队形和二维矩形晶格队形有显著改进，其中二维菱形晶格提供的流体动力益处最大。一般来说，我们这种自洽的建模框架可能广泛适用于集体动力学主要由流体介导的记忆驱动的活性系统。
Fish schools and bird flocks exhibit complex collective dynamics whose self-organization principles are largely unknown. The influence of hydrodynamics on such collectives has been relatively unexplored theoretically, in part due to the difficulty in modeling the temporally long-lived hydrodynamic interactions between many dynamic bodies. We address this through a novel discrete-time dynamical system (iterated map) that describes the hydrodynamic interactions between flapping swimmers arranged in one- and two-dimensional lattice formations. Our 1D results exhibit good agreement with previously published experimental data, in particular predicting the bistability of schooling states and new instabilities that can be probed in experimental settings. For 2D lattices, we determine the formations for which swimmers optimally benefit from hydrodynamic interactions. We thus obtain the following hierarchy: while a side-by-side single-row "phalanx" formation offers a small improvement over a solitary swimmer, 1D in-line and 2D rectangular lattice formations exhibit substantial improvements, with the 2D diamond lattice offering the largest hydrodynamic benefit. Generally, our self-consistent modeling framework may be broadly applicable to active systems in which the collective dynamics is primarily driven by a fluid-mediated memory.