Dipolophoresis in concentrated suspensions of ideally polarizable spheres
Dipolophoresis in concentrated suspensions of ideally polarizable spheres
复制标题
理想极化球体浓缩悬浮液中的介电电泳
DOI：
--
复制
发表时间：
2019
影响因子：
3.7
通讯作者：
J. S. Park
中科院分区：
文献类型：
--
作者：
S. Mirfendereski;J. S. Park
利用大规模数值模拟方法，分析了在非线性电动现象影响下，理想极化球形颗粒在浓悬浮液中的动力学行为。粒子被假定为不携带净电荷，并被认为经历介电泳和诱导电荷电泳的组合，称为偶极电泳。已知混沌运动和由此产生的流体动力学扩散由诱导电荷电泳驱动，诱导电荷电泳主导介电电泳。高达体积分数$unicode[STIX]{x1 D 719}约35，\%$，粒子动力学似乎是阻碍了排除体积与浓度的相互作用的大小的增加。然而，一个非平凡的悬浮液行为中观察到的集中制度，其中流体动力学扩散系数开始增加与体积分数在$unicode[STIX]{x1 D 719}约35，\%$，达到局部最大值之前，然后急剧下降，接近随机紧密堆积。类似的非平凡的行为中观察到的粒子速度和数量密度波动的体积分数，在其中观察到的非平凡的行为的流体动力学扩散。我们解释这些非平凡的行为作为一个结果的粒子接触，这是相关的粒子配对的主导机制。根据接触的性质，将粒子接触分为吸引接触和排斥接触两类，特别是当$unicode[STIX]{x1 D 719}>20，\%$时，强排斥接触占主导地位.此外，这种转变是可见的对分布函数，这也揭示了在集中制度的悬浮液微观结构的变化。看来，强大的和大规模的排斥接触沿着垂直于电场的方向，促进非平凡的悬浮行为中观察到的集中制度。
The dynamics of ideally polarizable spherical particles in concentrated suspensions under the effects of nonlinear electrokinetic phenomena is analysed using large-scale numerical simulations. Particles are assumed to carry no net charge and considered to undergo the combination of dielectrophoresis and induced-charge electrophoresis termed dipolophoresis. Chaotic motion and resulting hydrodynamic diffusion are known to be driven by the induced-charge electrophoresis, which dominates the dielectrophoresis. Up to a volume fraction $unicode[STIX]{x1D719}approx 35,\%$ , the particle dynamics seems to be hindered by the increase in the magnitude of excluded volume interactions with concentration. However, a non-trivial suspension behaviour is observed in concentrated regimes, where the hydrodynamic diffusivity starts to increase with the volume fraction at $unicode[STIX]{x1D719}approx 35,\%$ , before reaching a local maximum, and then drastically decreases on approaching random close packing. Similar non-trivial behaviours are observed in the particle velocity and number-density fluctuations around volume fractions at which the non-trivial behaviour of the hydrodynamic diffusion is observed. We explain these non-trivial behaviours as a consequence of particle contacts, which are related to the dominant mechanism of particle pairings. The particle contacts are classified into attractive and repulsive classes by the nature of contacts, and in particular, the strong repulsive contact becomes predominant at $unicode[STIX]{x1D719}>20,\%$ . Moreover, this transition is visible in the pair distribution functions, which also reveal the change in the suspension microstructure in concentrated regimes. It appears that strong and massive repulsive contacts along the direction perpendicular to an electric field promote the non-trivial suspension behaviours observed in concentrated regimes.