Inertia- And shear-induced inhomogeneities in non-Brownian mono and bidisperse suspensions under wall-bounded linear shear flow

Abstract

The effect of finite inertia on the particle distribution of mono and bidisperse suspensions under a wall-bounded linear shear flow has been numerically studied using lattice Boltzmann simulations in the range of the particle Reynolds number (Rep) up to approximately 1 at moderate volume fractions (φ ¯ = 0.2). We found that the channel-to-particle size ratio (H / a p) plays an important role in the monodisperse particle distribution at R e p > 0.1, such that the particles with H / a p = 19 maintain a uniform distribution even at finite inertia, while those with H / a p = 32 accumulate in the mid-plane, and the accumulation increases with increasing H / a p and decreasing φ ¯. The bidisperse particle suspension comprising a mixture of large (H / a l = 19) and small (H / a s = 32) particles with φ l ¯ = 0.05 and φ s ¯ = 0.15 was also examined, where the subscripts l and s denote large and small particles, respectively. The particle distribution of the mixture was strikingly different from that expected for monodisperse suspensions, such that the net migration of large particles was reversed toward the walls at R e s > 0.1. Further, it was demonstrated that the inertia-driven concentration gradient of small particles leads to the diffusiophoretic migration of large particles moving toward the walls.