DYNAMIC SIMULATION OF BIMODAL SUSPENSIONS OF HYDRODYNAMICALLY INTERACTING SPHERICAL-PARTICLES
DYNAMIC SIMULATION OF BIMODAL SUSPENSIONS OF HYDRODYNAMICALLY INTERACTING SPHERICAL-PARTICLES
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DOI：
10.1017/s0022112093001697
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发表时间：
1993-08-01
影响因子：
3.7
通讯作者：
POWELL, RL
中科院分区：
文献类型：
--
作者：
CHANG, CY;POWELL, RL
斯托克斯动力学用于模拟单层双峰分布球形颗粒悬浮液在简单剪切流下的动力学。仅考虑水动力。多体远场效应是使用大迁移率矩阵的逆来计算的。近场效应是根据两个大小不等的球体之间相互作用的精确方程计算得出的。详细的微观结构（例如成对分布函数和簇形成）和相对粘度都是针对粒径比为 2 和 4 的双峰悬浮液确定的。通过将 25、49、64 和 100 个颗粒视为无限周期阵列的“一个”单元来模拟“无限”悬浮液的流动。检查了不同尺寸颗粒的尺寸比和相对分数的影响。当面积分数 phi(a) 小于 0.4 时，粒度分布不会影响计算的粘度。对于 phi(a) > 0.4，并且对于小球体的固定比例，双峰悬浮液通常比单分散悬浮液具有更低的粘度，并且这种效应的大小随着 phi(a) 的增加而增加。当 phi(a) 和体积分数 phi(v) 分别通过二维和三维的最大堆积值标准化时，这些结果与实验结果相当。在微观结构水平上，粘度降低与颗粒尺寸分布对簇中颗粒平均数量的影响有关。在固定面积分数下，较小颗粒的存在往往会降低平均簇尺寸，特别是在较大的 phi(a) 下，观察到粘度显着降低。由于单分散悬浮液中大簇的存在与高粘度直接相关，因此这为双峰悬浮液中粘度降低提供了动态机制。
Stokesian dynamics is used to simulate the dynamics of a monolayer of a suspension of bimodally distributed spherical particles subjected to simple shearing flow. Hydrodynamic forces only are considered. Many-body far-field effects are calculated using the inverse of the grand mobility matrix. Near-field effects are calculated from the exact equations for the interaction between two unequal-sized spheres. Both the detailed microstructure (e.g. pair-distribution function and cluster formation) and the relative viscosity are determined for bimodal suspensions having particle size ratios of 2 and 4. The flow of an 'infinite' suspension is simulated by considering 25, 49, 64, and 100 particles to be 'one' cell of an infinite periodic array. The effects of both the size ratio and the relative fractions of the different-sized particles are examined. When the area fraction, phi(a), is less than 0.4 the particle size distribution does not affect the calculated viscosity. For phi(a) > 0.4, and for a fixed fraction of small spheres, the bimodal suspensions generally have lower viscosities than monodispersed suspensions, with the size of this effect increasing with phi(a). These results compare favourably with experiment when phi(a) and the volume fraction, phi(v), are normalized by the maximum packing values in two and three dimensions, respectively. At the microstructural level, viscosity reduction is related to the influence of particle size distribution on the average number of particles in clusters. At a fixed area fraction, the presence of smaller particles tends to reduce average cluster size, particularly at larger phi(a), where significant viscosity reductions are observed. Since the presence of large clusters in monodispersed suspensions has been directly linked to high viscosities, this provides a dynamic mechanism for the viscosity reduction in bimodal suspensions.