Utilizing the Discrete Element Method for the Modeling of Viscosity in Concentrated Suspensions

Abstract

The rheological behavior of concentrated suspensions is a complicated problem because it originates in the collective motion of particles and their interaction with the surrounding fluid. For this reason, it is difficult to accurately model the effect of various system parameters on the viscosity even for highly simplified systems. We model the viscosity of a hard-sphere suspension subjected to high shear rates using the dynamic discrete element method (DEM) in three spatial dimensions. The contact interaction between particles was described by the Hertz model of elastic spheres (soft-sphere model), and the interaction of particles with flow was accounted for by the two-way coupling approach. The hydrodynamic interaction between particles was described by the lubrication theory accounting for the slip on particle surfaces. The viscosity in a simple-shear model was evaluated from the force balance on the wall. The obtained results are in close agreement with literature data for systems with hard spheres. Namely, the viscosity is shown to be independent of shear rate and primary particle size for monodisperse suspensions. In accordance with theory and experimental data, the viscosity grows rapidly with particle volume fraction. We show that this rheological behavior is predominantly caused by the lubrication forces. A novel approach based on the slip of water on a particle surface was developed to overcome the divergent behavior of lubrication forces. This approach was qualitatively validated with literature data from AFM measurements using a colloidal probe. The model presented in this work represents a new, robust, and versatile approach to the modeling of viscosity in suspensions with the possibility to include various interaction models and study their effect on viscosity.

Slip on a particle surface as the possible origin of shear thinning in non-Brownian suspensions

“…20,21,[24][25][26][27][28] As we demonstrate later, for concentrated suspensions, the local shear rate g between a pair of particles can be much larger (by orders of magnitude) than the imposed shear rate G (e.g., in a simple shear flow). Together with our recent finding that the increasing slip length causes the suspension viscosity to decrease, 29 this suggests that the surface slip might be responsible for the viscosity decrease with the increasing shear rate.…”

Modeling Red Blood Cell Viscosity Contrast Using Inner Soft Particle Suspension

“…For colloidal suspensions [ 38 , 39 ], the models treat particles as hard or soft spheres with lubrication forces suspended in a fluid. The modelling of particle behaviour involves tracking their position, mass and rotational inertia that enter the Newton motion equations together with lubrication forces.…”

Finite Element Study on the Wear Performance of Movable Jaw Plates of Jaw Crushers after a Symmetrical Laser Cladding Path

“…In this study, WDB620 (Figure 1) was selected as the material of the moving jaw plate, and then the ceramic powder was laser-cladded on the surface of the moving jaw plate. The contents of various chemical components of ceramic powder are shown in Table 1 [22][23][24][25]. The cylinder sample after cutting is installed on the friction electronic tester and closely contacts with the ring.…”