Numerical study on the inertial effects of particles on the rheology of a suspension

Abstract

Einstein’s viscosity formula is only applicable for dilute suspensions in which hydrodynamic interactions or inertial effects are sufficiently negligible. Therefore, the contribution of hydrodynamic interactions or the effects of inertia on the rheology of suspensions should be investigated. In order to evaluate the inertial effects of microscopic particles on the macroscopic rheology of a suspension, pressure-driven flow simulations with various confinements and Reynolds numbers were performed by a two-way coupling scheme. The results showed that the relative viscosity of the suspension decreases with increase in the particle size even when the concentration of the suspension remains the same. The results also indicated that the confinement should be less than 0.02 when applying Einstein’s viscosity formula. Moreover, the relative viscosity of the suspension under a high Reynolds number condition increases because of outward particle migration, and the non-Newtonian property of the suspension changes from thixotropy to dilatancy. Suspension is a potential fluid because its macroscopic rheological properties are altered owing to suspended particles’ behavior, that is, its microstructure. It can be stated that inertia is one of the promising factors to control suspension rheology.