Computer Simulation of Flow Behaviors of Concentrated Suspensions

点击翻译按钮获取中文摘要

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.