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arXiv 2108.07261cond-mat.soft
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$K$ -剪切增稠悬浮液的岩心分析

$K$-core analysis of shear-thickening suspensions

Omer Sedes, Bulbul Chakraborty, Hernan A. Makse, Jeffrey F. Morris

摘要:

悬浮液的剪切增稠研究了离散粒子模拟,占流体动力学,排斥力和接触力。当施加的剪切应力$σ$能够克服排斥力时,包括摩擦力在内的接触力被激活。模拟方法捕获强连续和不连续的剪切增稠(CST和DST)的固体体积分数$0.54 \le ϕ\le 0.56$的范围内研究这里。这项工作提出了接触力网络的特点,在剪切下的悬浮开发。每个颗粒的摩擦接触$Z$的数量示出有一个一对一的关系与悬浮应力,和摩擦接触的简单渗流的条件被发现偏离强烈的随机网络模型。的应力被证明具有重要的相关性与拓扑不变度量的接触网络称为$k$ -核心;的$k$ -核心是最大的子图(“集群”),其中所有成员粒子有$k$或更多的摩擦接触到其他成员的同一子图。在固体体积分数为$ϕ\le 0.56$的情况下,本研究中仅发现了$k\le 3$。悬浮液的流变性和$k$ -核心之间的独特的关系被发现。一个是应力敏感性,定义为$\partial σ/\partial \dotγ$,其中$\dotγ$是剪切速率,被发现在$3$ -核心的起始条件下达到峰值,无论该系统是否表现出CST或DST。第二,在DST开始时,不同$k$的核内的每个颗粒的应力随着$k$的增加而急剧增加;在CST中,差异是轻微的。

英文摘要:

Shear thickening of suspensions is studied by discrete-particle simulation, accounting for hydrodynamic, repulsive, and contact forces. The contact forces, including friction, are activated when the imposed shear stress $σ$ is able to overcome the repulsive force. The simulation method captures strong continuous and discontinuous shear thickening (CST and DST) in the range of solid volume fraction $0.54 \le ϕ\le 0.56$ studied here. This work presents characteristics of the contact force network developed in the suspension under shear. The number of frictional contacts per particle $Z$ is shown to have a one-to-one relationship with the suspension stress, and the conditions for simple percolation of frictional contacts are found to deviate strongly from those of a random network model. The stress is shown to have important correlations with topological invariant metrics of the contact network known as $k$-cores; the $k$-cores are maximal subgraphs (`clusters') in which all member particles have $k$ or more frictional contacts to other members of the same subgraph. Only $k\le 3$ is found in this work at solid volume fractions $ϕ\le 0.56$. Distinct relationships between the suspension rheology and the $k$-cores are found. One is that the stress susceptibility, defined as $\partial σ/\partial \dotγ$ where $\dotγ$ is the shear rate, is found to peak at the condition of onset of the $3$-core, regardless of whether the system exhibits CST or DST. A second is that the stress per particle within cores of different $k$ increases sharply with increase of $k$ at the onset of DST; in CST, the difference is mild.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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