Dynamics of concentrated suspensions of non-colloidal particles in Couette flow

Fully three-dimensional numerical simulations of concentrated suspensions of 0(1000) particles in a Couette flow at zero Reynolds number are performed with the goal of determining the wall effects on concentrated suspensions of non-colloidal particles. The simulations, based on the force-coupling method, are performed for 0.2 <= phi <= 0.4 and 10 < L-y/a < 30, where phi denotes the volume fraction and L-y and a are, respectively, the channel height and the particle radius. It is shown that the suspensions can be divided into three regions depending on the microstructures; the wall region where a structured particle layering is dominant, the core region in which the suspension field is quasi-homogeneous, and the buffer region which shows the characteristics of both the particle layer and the shear structure. The width of the inhomogeneous region (wall and buffer) is a function of phi and not sensitive to L-y/a, once L-y/a is larger than a threshold. Rheological properties in the inhomogeneous and quasi-homogeneous regions are investigated. The particle stresses are compared with previous rheological models.