Influence of Oseen’s correction on fine particle settling velocity formula for bidisperse suspension

In this paper, a simplified cellular model of particle sedimentation under gravity in bidisperse suspension is proposed. To determine the average settling velocity of fine particles, their residence time in the cylindrical cell surrounding the large ones is evaluated. The flow field of a viscous incompressible fluid around the large particle is described based on the approximate Oseen solution. The fine particles are assumed to be inertialless, which allows one to determine the trajectory of these particles by solving only kinematic equations. The influence of the Reynolds number and the size of the cylindrical cell on the average velocity of the fine particles is assessed. A formula for determining the sedimentation velocity of fine particles settling in the presence of large ones with allowance for the volume fraction of coarse particles, particle size ratio, and the Reynolds number is derived. It is shown that the increase in the Reynolds number tends to reduce the effect of the particle size ratio on the average sedimentation velocity of fine particles.