This work studies the aggregation of colloids under depletion attraction focusing on the effect of hydrodynamic interactions on cluster kinetics and average structures. Our numerical study is based on a variant of the immersed boundary method (inertial coupling method) which solves the solvent fluctuating hydrodynamics and instantaneously couple the particle and the fluid momentum transfer. Comparison is made with Langevin Dynamics and Monte Carlo methods, which do not include hydrodynamics. We consider a small system (20 and 40 particles) which reproduces the system considered by Whitmer and Luijten [J. Chem. Phys. B, 115 (22) 2011] (analyzed by multiparticle rotation dynamics). In that work, the authors report substantial hydrodynamic effects altering the cluster sizes and shapes. By contrast, within statistical error, we have not found any hydrodynamic effect on the average clusters structure. We also analyze the time-evolution of the aggregation kinetics, revealing a slowing down of the process due to the reduction of the mobility close to the clusters. The time correlation of the cluster number, shape and size reveals two characteristic times: a decay at short times faster than the single particle diffusion time $t_D$, followed by a slower exponential decay at long times with a typical time of several $t_D$.

中文翻译：

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水动力对稀悬浮液中具有短程耗尽潜能的胶体聚集的影响

这项工作研究了在耗尽吸引下胶体的聚集，重点是流体动力学相互作用对团簇动力学和平均结构的影响。我们的数值研究基于沉浸边界方法（惯性耦合方法）的一种变体，该方法解决了溶剂波动的流体动力学问题，并瞬时耦合了颗粒和流体动量传递。用Langevin动力学和Monte Carlo方法进行了比较，它们不包括流体动力学。我们考虑一个小的系统（20和40个粒子），该系统再现了Whitmer和Luijten所考虑的系统[J. 化学 物理 B，115（22）2011]（通过多粒子旋转动力学分析）。在那项工作中，作者报告了改变团簇大小和形状的巨大水动力效应。相比之下，在统计误差范围内，我们还没有发现对平均团簇结构有任何流体动力作用。我们还分析了聚集动力学的时间演化，揭示了由于靠近簇的迁移率降低而导致的过程减慢。团簇数目，形状和大小的时间相关性揭示了两个特征时间：在短时间内的衰变比单个粒子扩散时间快${Ť}_d$，然后在较长的时间内（通常为几倍）缓慢的指数衰减 ${Ť}_d$。