The effect of liquid viscosity on sheared granular flows

This work investigates the effect of transport properties in sheared granular flows with adding different silicone oils. We performed a series of experiments in a shear cell device using 2-mm soda lime beads as the granular materials by adding little amount of different silicone oils. The viscosity of silicone oils added was changed in different tests. By particle tracking method, the velocities, the velocity fluctuations and the self-diffusion coefficients were measured and analyzed. It was found that for the granular system with adding the more viscous silicone oil, the system became less active due to the greater shear force and cohesive force, which resulted in the decrease of velocity fluctuations and diffusions. Three bi-directional stress gages were installed to the upper wall to measure the normal and shear stresses of the granular materials along the upper wall. Thus, the effective viscosities of the wet granular material systems could be evaluated. The dimensionless normal and shear stresses, and the effective viscosity in the wet sheared granular flow were found to decrease with the increase of the viscosity of the added silicone oil. The influence of the viscosity of added fluid on these transport properties of wet granular systems will be discussed.