Viscous resuspension in a bidensity suspension

Experiments were performed in a narrow gap Couette device to study the visc ous resuspension process in a bidensity suspension consisting of two types of spherical particles, both having the same size, one of which was heavy, while the other had the same density as that of the suspending fluid. The r esuspension height of an initially settled bed of heavy particles was measu red over a ten-fold range of applied shear rates, using an imaging techniqu e which was developed to study the particle migration process in concentrat e bidisperse suspensions. It was found that, at a given shear rate, the res uspension height of the heavy particles increased with an increase in the c oncentration of the neutrally buoyant spheres. The experimental results wer e then compared with the predictions of a bidensity model based on the part icle migration theory of previous work, and good agreement was found betwee n the two. (C) 1999 Elsevier Science Ltd. All rights reserved.