A general constitutive model for dense, fine-particle suspensions validated in many geometries
A general constitutive model for dense, fine-particle suspensions validated in many geometries
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DOI：
10.1073/pnas.1908065116
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发表时间：
2019-10-15
影响因子：
11.1
通讯作者：
Kamrin, Ken
中科院分区：
文献类型：
--
作者：
Baumgarten, Aaron S.;Kamrin, Ken
细颗粒悬浮液（如玉米淀粉与水的混合物）在剪切时表现出粘度的巨大变化，产生令人着迷的行为，吸引了儿童和流变学家。在简单流动几何形状中对这些混合物的检查表明，粒间排斥及其对颗粒接触摩擦性质的影响是这种效应的核心-对于静止或缓慢剪切的混合物，排斥会阻止颗粒之间形成摩擦接触，而当剪切更有力时，颗粒应力克服排斥力，使颗粒能够摩擦相互作用并形成抵抗流动的微观结构。这些混合物以前的本构研究集中在特定的情况下，通常限于二维，稳定，简单的剪切流。在这项工作中，我们介绍了一个预测和一般，这种材料的三维连续模型，使用混合物理论耦合的流体和颗粒相。在模型中发挥核心作用，我们引入了一个微观结构状态变量，其演变推导出小规模的物理参数，并检查与现有的数据。我们的空间和时间相关模型在各种不稳定、非均匀流配置中进行了数值实现，结果表明，该模型可以准确捕获各种关键行为：1）在定常流动中观察到的连续剪切增稠（CST）和不连续剪切增稠（DST）行为，2）“剪切干扰锋”的时间依赖性传播，3）“碰撞激活干扰前沿”的时间依赖性传播，以及4）非牛顿的“运行在欧布莱克”效应，其中快速运动保持漂浮而慢速运动下沉。
Fine-particle suspensions (such as cornstarch mixed with water) exhibit dramatic changes in viscosity when sheared, producing fascinating behaviors that captivate children and rheologists alike. Examination of these mixtures in simple flow geometries suggests intergranular repulsion and its influence on the frictional nature of granular contacts is central to this effect-for mixtures at rest or shearing slowly, repulsion prevents frictional contacts from forming between particles, whereas when sheared more forcefully, granular stresses overcome the repulsion allowing particles to interact frictionally and form microscopic structures that resist flow. Previous constitutive studies of these mixtures have focused on particular cases, typically limited to 2D, steady, simple shearing flows. In this work, we introduce a predictive and general, 3D continuum model for this material, using mixture theory to couple the fluid and particle phases. Playing a central role in the model, we introduce a microstructural state variable, whose evolution is deduced from small-scale physical arguments and checked with existing data. Our space- and time-dependent model is implemented numerically in a variety of unsteady, nonuniform flow configurations where it is shown to accurately capture a variety of key behaviors: 1) the continuous shear-thickening (CST) and discontinuous shear-thickening (DST) behavior observed in steady flows, 2) the time-dependent propagation of "shear jamming fronts," 3) the time-dependent propagation of "impactactivated jamming fronts," and 4) the non-Newtonian, "running on oobleck" effect, wherein fast locomotors stay afloat while slow ones sink.