Abstract The aggregation of spherical nanoparticles as they propagate through porous media is explored using lattice Boltzmann simulations and tracking of the trajectoties of individual particles. The porous media are modeled as periodic arrays of spheres in different packing configurations. The effects of interparticle interactions on particle aggregation are treated through a single aggregation probability upon particle collision. Fast aggregation is represented by an aggregation probability with values close to one, and slow aggregation is represented by lower aggregation probability. An algorithm that accounts for the different time scales between hydrodynamics and Brownian motion is devised and validated. It is found that primary particle size, initial particle concentration, injection flow rate, and aggregation probability significantly impact the dynamics of the aggregation. Calculations of the transient mean size of the aggregates show that the aggregation rate is high near the entrance of the porous medium, yet dramatically decreases when moving farther downstream. The reason is that the growth of larger aggregates slows the aggregation process. It is also found that the bigger aggregates are formed in the pore space near the pore matrix surface, where particle residence time is long enough to allow the aggregates to grow. An empirical correlation based on measurable parameters is proposed for the prediction of the mean aggregate size.

中文翻译：

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多孔介质中纳米颗粒聚集的流体动力学效应

摘要 使用晶格玻尔兹曼模拟和跟踪单个粒子的轨迹来探索球形纳米粒子在通过多孔介质传播时的聚集。多孔介质被建模为不同填充配置的周期性球体阵列。通过粒子碰撞时的单个聚集概率来处理粒子间相互作用对粒子聚集的影响。快速聚合用值接近 1 的聚合概率表示，慢聚合用较低的聚合概率表示。设计并验证了一种算法，该算法考虑了流体动力学和布朗运动之间的不同时间尺度。发现初级粒径、初始颗粒浓度、注射流速、和聚合概率显着影响聚合的动态。聚集体瞬时平均尺寸的计算表明，在多孔介质入口附近聚集率很高，但在向下游移动时显着降低。原因是较大聚集体的生长减慢了聚集过程。还发现在孔隙基质表面附近的孔隙空间中形成较大的聚集体，在那里颗粒停留时间足够长以允许聚集体生长。提出了基于可测量参数的经验相关性来预测平均聚集体尺寸。但在向下游移动时会急剧下降。原因是较大聚集体的生长减慢了聚集过程。还发现在孔隙基质表面附近的孔隙空间中形成较大的聚集体，在那里颗粒停留时间足够长以允许聚集体生长。提出了基于可测量参数的经验相关性来预测平均聚集体尺寸。但在向下游移动时会急剧下降。原因是较大聚集体的生长减慢了聚集过程。还发现在孔隙基质表面附近的孔隙空间中形成较大的聚集体，在那里颗粒停留时间足够长以允许聚集体生长。提出了基于可测量参数的经验相关性来预测平均聚集体尺寸。