We investigate a system of co-oriented active particles interacting only via hydrodynamic and steric interactions in a two-dimensional fluid. We offer a new method of calculating the flow created by any active particle in such a fluid, focusing on the dynamics of flow fields with a high-order spatial decay, which we analyze using a geometric Hamiltonian. We show that when the particles are oriented and the flow has a single, odd power decay, such systems lead to stable, fractal-like aggregation, with the only exception being the force dipole. We discuss how our results can easily be generalized to more complicated force distributions and to other effective two-dimensional systems.

中文翻译：

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二维定向活性颗粒的流体动力诱导聚集

我们研究了仅通过二维流体中的流体动力学和空间相互作用相互作用的共取向活性粒子系统。我们提供了一种计算此类流体中任何活性粒子产生的流动的新方法，重点关注具有高阶空间衰减的流场动力学，我们使用几何哈密顿量对其进行分析。我们表明，当粒子定向且流动具有单一的奇数功率衰减时，此类系统会导致稳定的分形聚集，唯一的例外是力偶极子。我们讨论如何将我们的结果轻松推广到更复杂的力分布和其他有效的二维系统。