Prediction of Viscosity of Slurry Suspended Fine Particles Using Coupled DEM-DNS Simulation

Prediction of the apparent viscosity of a slurry suspended fine particles is important for developing slurry-treating processes. After Einstein’s formulation for the apparent viscosity of a dilute, completely dispersed slurry, several viscosity equations were proposed. However, viscosity depends not only on the volume fraction of solid particles but also on many factors such as particle shape, particle interaction, the aggregation structure of suspended particles and the structure of fluid flow. A hybrid simulation employing the distinct element method (DEM) and the direct numerical simulation method (DNS) was developed to obtain the relation between these factors and the apparent viscosity of slurry suspended fine particles. The apparent viscosity of a completely dispersed slurry obtained by the simulation is in good agreement with the experimental and calculated values obtained by the empirical equations. Shear-thinning behavior due to the collapse of agglomerates with increase in mean shear rate was observed for the case of a slurry with agglomerated particles. This behavior was caused by the existence of so-called immobile water in the agglomerates. The influences of the shape of aggregation and particle interaction on the apparent viscosity are investigated by the simulation.