Mixing of cohesive particles in a shear cell

This paper discusses a series of experiments performed in a shear cell device with six different amounts of silicone oils and using 2-mm glass spheres as the granular materials. The motion of granular materials is recorded by a high-speed camera. Using the image processing technology and particle tracking method, the positions and velocities of particles are measured. The self-diffusion coefficient can be found from the history of the particle displacements. Mixing experiments are performed, and the developments of mixing layer thicknesses are measured. The measured mixing layer thicknesses are compared with the calculations from a simple diffusion equation using the data of apparent self-diffusion coefficients obtained from the current measurements. The comparisons show good agreements, demonstrating that the mixing process of granular materials occur through the diffusion mechanism in this cohesive sheared flow. In addition, the apparent self-diffusion coefficient decreases with the increasing liquid volume, indicating that cohesive forces between particles reduce granular mixing.