Tiwari Chandranshu, Singh Sunil P
Department of Physics, Indian Institute of Science Education and Research, Bhopal 462 066, Madhya Pradesh, India.
Soft Matter. 2024 Jun 20;20(24):4816-4826. doi: 10.1039/d4sm00044g.
In this article, we present the collective dynamics of active dumbbells in the presence of a static circular obstacle using Brownian dynamics simulation. The active dumbbells aggregate on the surface of a circular obstacle beyond a critical radius. The aggregation is non-uniform along the circumference, and the aggregate size increases with the activity (Pe) and the curvature radius (). The dense aggregate of active dumbbells displays persistent rotational motion with a certain angular speed, which linearly increases with activity. Furthermore, we show a strong polar ordering of the active dumbbells within the aggregate. The polar ordering exhibits long-range correlation, with the correlation length corresponding to the aggregate size. Additionally, we show that the residence time of an active dumbbell on the obstacle surface increases rapidly with area fraction due to many-body interactions that lead to a slowdown of the rotational diffusion. This article further considers the dynamical behavior of a tracer particle in the solution of active dumbbells. Interestingly, the speed of the passive tracer particle displays a crossover from monotonically decreasing to increasing with the size of the tracer particle upon increasing the dumbbells' speed. Furthermore, the effective diffusion of the tracer particle displays non-monotonic behavior with the area fraction; the initial increase in diffusivity is followed by a decrease for a larger area fraction.
在本文中，我们使用布朗动力学模拟展示了在存在静态圆形障碍物的情况下活性哑铃的集体动力学。活性哑铃在超过临界半径时聚集在圆形障碍物表面。聚集沿圆周不均匀，且聚集体尺寸随活性（皮克莱数）和曲率半径增加。活性哑铃的密集聚集体以一定角速度呈现持续旋转运动，该角速度随活性线性增加。此外，我们展示了聚集体内活性哑铃的强极性排序。极性排序呈现长程相关性，相关长度对应于聚集体尺寸。此外，我们表明由于多体相互作用导致旋转扩散减慢，活性哑铃在障碍物表面的停留时间随面积分数迅速增加。本文进一步考虑了示踪粒子在活性哑铃溶液中的动力学行为。有趣的是，随着哑铃速度增加，被动示踪粒子的速度呈现出从随示踪粒子尺寸单调递减到递增的转变。此外，示踪粒子的有效扩散随面积分数呈现非单调行为；扩散率最初增加，随后在较大面积分数时下降。
