Stresses and transport phenomena in sheared granular flows with different wall conditions

Abstract

Experiments were performed in a shear cell device with four different wall conditions. The glass spheres with a mean diameter of 3 mm were used as granular materials. Three bidirectional stress gauges were installed to measure the normal and shear stresses along the upper wall. The motions of the granular materials were recorded by a high-speed camera. The image processing technology and particle tracking method were employed to measure the average and fluctuation velocities in the streamwise and the transverse directions. By tracking the movements of particles continually, the variation in the mean-square diffusive displacements with time was plotted and the self-diffusion coefficient was determined. The self-diffusion coefficients in the streamwise direction were much higher than those in the transverse direction. The self-diffusion coefficients were increased with the increase of the velocity fluctuations, the shear rates, and the stresses. The influences of the wall conditions (wall frictional coefficients) on these properties are discussed in the paper.