HYDRODYNAMIC PARTICLE MIGRATION IN A CONCENTRATED SUSPENSION UNDERGOING FLOW BETWEEN ROTATING ECCENTRIC CYLINDERS

We report on experimental measurements and numerical predictions of sh ear-induced migration of particles in concentrated suspensions subject ed to flow in the wide gap between a rotating inner cylinder placed ec centrically within a fixed outer cylinder (a cylindrical bearing). The suspensions consist of large noncolloidal spherical particles suspend ed in a viscous Newtonian liquid. Nuclear magnetic resonance imaging i s used to measure the time evolution of concentration and velocity pro files as the flow induces particle migration from the initial well-mix ed state. The experimental results are compared against numerical pred ictions for the concentration and velocity profiles. The coupled equat ions of motion and particle migration are solved numerically for a gen eralized Newtonian fluid with concentration-dependent viscosity with a n explicit pseudotransient finite volume code. While not all of the qu alitative features of the flow field are reproduced by the model, ther e is acceptable overall agreement with the experimental data.