The kinetics of flowing dispersions. VII. Oscillatory behavior of rods and discs in shear flow

Abstract

Damped oscillations of the orientation distributions of rods and discs were measured in the early stages of shearing. As a result of the spread in the particle axis ratio and of particle interactions, equilibrium orientation distributions were established in the plane normal to the vorticity axis after a few particle rotations. Oscillations of the distribution of phase angles imposed on a monotonic change due to particle interactions were also observed. The reciprocal of the measured relaxation times of the decrement of oscillations of the mean projections of rods varied linearly with the particle concentration, in good agreement with theory. It was concluded that rotary Brownian motion of the particles played a negligible role in the experiments. The theory and supporting experimental data provide methods for a priori predictions of constitutive equations of the non-Newtonian rheological properties of dilute suspensions.