Two-dimensional dynamics and microstructure of dense suspensions of ideally polarizable particles in an electric field: The nontrivial effect of confinement.

IF 2.4 3区 物理与天体物理 Q1 Mathematics
Seyed Mohammad Hosseini, Siamak Mirfendereski, Jae Sung Park
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引用次数: 0

Abstract

The dynamics and microstructure of two-dimensional suspensions of ideally polarizable particles in an electric field are studied using large-scale numerical simulations. The particles are assumed to carry no net charge and thus known to undergo a nonlinear electrokinetic phenomenon termed dipolophoresis-the combination of dielectrophoresis and induced-charge electrophoresis. For ideally polarizable particles, the effect of induced-charge electrophoresis is dominant, which results in chaotic and diffusive motions. Up to an area fraction ϕ≈50%, the diffusive particle dynamics get hindered due to increasing excluded volume interactions. At ϕ=50%, the suspension intermittently exhibits a nearly frozen state, resembling a static equilibrium state, which arises only at this area fraction. A nonmonotonic behavior is then observed in the suspension dynamics, where the hydrodynamic diffusivity starts to increase with the area fraction and reaches a local maximum at ϕ=60% before decreasing again as approaching random close packing. We illuminate this nonmonotonic suspension dynamics in connection to the transition in particle contact mechanisms and suspension microstructure. Furthermore, the effects of confinement on suspension dynamics and microstructure are examined, where another nonmonotonic and nontrivial behavior arises in terms of the level of confinement. Upon increasing confinement, velocity fluctuations indeed increase compared to its unbounded values and reach a maximum at moderate confinement before getting diminished at extreme confinement. This nonmonotonic and nontrivial behavior is the most prominent at ϕ=50%. We explain the nonmonotonic behavior as a consequence of symmetry breaking in particle interactions due to confinement, resulting in suspension instability. The confinement-induced instability causes the emergence of coherent vortical structures that lead to the formation of layering microstructure. The confinement-induced effects are well correlated with the level of chaos in a suspension. These results can offer the potential use of confinement to effectively manipulate such suspensions.

理想极化粒子密集悬浮液在电场中的二维动力学和微观结构:约束的非平凡效应。
采用大规模数值模拟方法研究了理想极化粒子在电场作用下的二维悬浮液的动力学和微观结构。假设这些粒子不带净电荷,因此已知会经历一种称为双极化的非线性电动力学现象,即介电电泳和诱导电荷电泳的结合。对于理想极化粒子,诱导电荷电泳的作用占主导地位,导致混沌和扩散运动。区域分数φ≈50%,扩散粒子动力学受到阻碍,由于增加排除的体积相互作用。在φ =50%时,悬浮液间歇性地呈现出几乎冻结的状态,类似于静态平衡状态,仅在此面积分数处出现。一个非单调的行为,然后在悬浮液动力学中观察到,其中流体动力扩散系数开始随着面积分数的增加而增加,并在φ =60%时达到局部最大值,然后在接近随机紧密堆积时再次下降。我们将这种非单调悬浮动力学与颗粒接触机制和悬浮微观结构的转变联系起来。此外,禁闭对悬架动力学和微观结构的影响进行了研究,其中禁闭水平产生了另一种非单调和非平凡的行为。在增加约束时,速度波动确实比其无界值增加,并在中等约束时达到最大值,然后在极端约束时减小。这种非单调和非平凡的行为在φ =50%时最为突出。我们将非单调行为解释为由于约束而导致的粒子相互作用对称性破缺的结果,从而导致悬浮不稳定。约束引起的不稳定性导致相干涡结构的出现,从而导致层状微观结构的形成。禁锢诱导的效应与悬浮液的混沌程度密切相关。这些结果可以提供约束的潜在用途,以有效地操纵这种悬浮液。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Physical review. E
Physical review. E 物理-物理:流体与等离子体
CiteScore
4.60
自引率
16.70%
发文量
0
审稿时长
3.3 months
期刊介绍: Physical Review E (PRE), broad and interdisciplinary in scope, focuses on collective phenomena of many-body systems, with statistical physics and nonlinear dynamics as the central themes of the journal. Physical Review E publishes recent developments in biological and soft matter physics including granular materials, colloids, complex fluids, liquid crystals, and polymers. The journal covers fluid dynamics and plasma physics and includes sections on computational and interdisciplinary physics, for example, complex networks.
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