Computer Simulation of Flow Behaviors of Concentrated Suspensions

浓缩悬浮液表现出复杂的流变特性，如触变性和流变性。根据传统的胶体科学，这些行为是由内部“结构”的某种变化引起的。然而，究竟形成了什么样的“结构”，以及它与流变性能有怎样的关系等基本问题还没有得到明确的回答。在这个项目中，我通过计算机模拟研究了剪切流中浓缩悬浮液的结构。研究了两种体系：硬球体系和聚合体系。在前一种情况下，流体动力相互作用是重要的，而在后一种情况下，接触胶体之间的凝聚力是必不可少的。针对每种情况，提出了一个新的模型来实现仿真。详细的结构和宏观流变资料。获取属性信息。一个特别有趣的结果是，在聚集球系统中，当浓度超过某一临界浓度时，球体形成无限大的网络，但粘度仍然是有限的。这表明骨料的粒度是决定粘度的关键因素。作为本研究的一个副产品，在浓乳剂中建立了一个新的理论，其中界面动力学是重要的。

Concentrated suspensions show complex rheological properties, such as thixotropy and rheopexy. According to traditional colloid science, these behaviors are caused by a certain change of internal "structure". However, basic questions such as what kind of "structure" is actually formed, and how it is related to rheological properties have not been answered clearly. In this project, I studied the structure of concentrated suspension in shear flow by computer simulation.Two systems are studied, the hard sphere system and the aggregating system. In the former case, the hydrodynamic interaction is important, and in the latter, the cohesive force between the touching colloids is essential. For each case, a new model is proposed to enable the simulation. The detailed information on the structure and the macroscopic rheological. properties are obtained. A particularly interesting result is that in the aggregating sphere system, the spheres form an infinitely large network when the concentration exceeds a certain critical concentration, but the viscosity remains finite. This indicates that the size of the aggregate is the key factor in determining the viscosity.As a byproduct of the present research, a new theory has been developed on the concentrated emulsions in which the dynamics of interface is important.