Ordered domains in sheared dense suspensions: The link to viscosity and the disruptive effect of friction
Ordered domains in sheared dense suspensions: The link to viscosity and the disruptive effect of friction
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DOI：
10.1122/8.0000453
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发表时间：
2022-02
影响因子：
3.3
通讯作者：
Abhay Goyal;E. Del Gado;Scott Z. Jones;N. Martys
中科院分区：
文献类型：
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作者：
Abhay Goyal;E. Del Gado;Scott Z. Jones;N. Martys
布朗胶体球的单分散悬浮液在高密度下结晶，并且在低于结晶阈值的密度下观察到剪切下的有序性。我们进行大规模的模拟模型悬浮液包含超过[公式：见正文]颗粒定量研究剪切下的有序性和调查其链接到悬浮液的流变性能。我们发现，在高速率下，对于[公式：见正文]，剪切流诱导了一个有序的转变，显着降低了测得的粘度。这种排序的分层和平面顺序的发展方面进行了分析，我们确定，颗粒被包装成六方晶体层（有许多缺陷），滑过去对方。通过计算本地[公式：见正文]和[公式：[见正文]序参数，我们确定的缺陷对应于链的粒子在一个squarelike晶格。我们计算了单个粒子对应力张量的贡献，发现剪切应力的最大贡献者主要位于这些密度较低的缺陷区域。缺陷结构使得能够形成颗粒的压缩链以抵抗剪切，但是这些链是瞬时的和短暂的。包含接触摩擦力允许应力承载结构生长成系统跨越网络，从而扰乱秩序并急剧增加悬浮液粘度。
Monodisperse suspensions of Brownian colloidal spheres crystallize at high densities, and ordering under shear has been observed at densities below the crystallization threshold. We perform large-scale simulations of a model suspension containing over [Formula: see text] particles to quantitatively study the ordering under shear and to investigate its link to the rheological properties of the suspension. We find that at high rates, for [Formula: see text], the shear flow induces an ordering transition that significantly decreases the measured viscosity. This ordering is analyzed in terms of the development of layering and planar order, and we determine that particles are packed into hexagonal crystal layers (with numerous defects) that slide past each other. By computing local [Formula: see text] and [Formula: see text] order parameters, we determine that the defects correspond to chains of particles in a squarelike lattice. We compute the individual particle contributions to the stress tensor and discover that the largest contributors to the shear stress are primarily located in these lower density, defect regions. The defect structure enables the formation of compressed chains of particles to resist the shear, but these chains are transient and short-lived. The inclusion of a contact friction force allows the stress-bearing structures to grow into a system-spanning network, thereby disrupting the order and drastically increasing the suspension viscosity.