Electrokinetic Lift of a Sphere Moving in Slow Shear Flow Parallel to a Wall: I. Experiment
Electrokinetic Lift of a Sphere Moving in Slow Shear Flow Parallel to a Wall: I. Experiment
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平行于壁在慢剪切流中运动的球体的动电升力：I. 实验
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
D. Prieve
中科院分区：
文献类型：
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作者：
S. Bike;L. Lazarro;D. Prieve
摘要 在本文中，我们展示了在不同粘度和电导率的溶液中，9.87 微米和 5.2 微米直径的聚苯乙烯乳胶球从壁上迁移的实验观察结果。在缓慢的线性剪切流期间，通过添加盐以增加电荷载体的数量或通过添加水以降低粘度而导致流体电导率的增加，从而减少了这种横向迁移。例如，在 6 s-1 的剪切速率下，观察到 5.2 μm 球体升力的最大电导率为 0.12 μS cm-1。此外，对于给定的流体电导率，在流动开始时颗粒-壁分离距离的增加通常随着颗粒zeta电位的增加而增加。这些观察结果支持了迁移是电动引起的假设，但基于当前润滑理论的升力预测比重力弱一个数量级以上。这种分歧导致我们在本文的后续部分中完善了动电升力理论。
Abstract In this paper we present experimental observations of the migration away from a wall of 9.87- and 5.2-μm-diameter polystyrene latex spheres in solutions of varying viscosity and conductivity. During slow linear shear flow, this lateral migration is diminished by an increase in the fluid conductivity caused either by adding salt to increase the number of charge carriers or by adding water to decrease the viscosity. At a shear rate of 6 s-1, for example, the largest conductivity for which lift of 5.2-μm spheres is observed is 0.12 μS cm-1. In addition, the increase in the particle-wall separation distance upon the initiation of flow generally increases with particle zeta potential for a given fluid conductivity. These observations support the hypothesis that the migration is electrokinetically induced, but predictions of lift based on the current lubrication theory are more than one order of magnitude weaker than gravity. This disagreement has led us to refine the electrokinetic lift theory in the sequel to this paper.