Influence of interstitial fluid viscosity on transport phenomenon in sheared granular materials

We report experimental measurements of transport properties on sheared granular materials with different interstitial fluids to study the granular flow behaviors. Four kinds of interstitial fluids are used in the experiments. The ensemble velocities, fluctuation velocities, granular temperature and self-diffusion coefficients are successfully measured by PTV method. The results indicate that the interstitial fluid plays an important role in determining the transport properties of the granular flow. The particles motions are more random and interactive collisions are more serious in a dry system (interstitial fluid of air). The values of fluctuations and granular temperatures are smaller as the interstitial fluid is more viscous resulting in the larger viscous force. The thickness of shear band is about three to eight particle diameters and increases with the decreasing interstitial fluid viscosity. The self-diffusion coefficient of granular materials is also discussed in this study. Both the self-diffusion coefficients and the granular temperature increase with the increasing shear rate. The average streamwise self-diffusion coefficient and granular temperature increase with the increase in Stokes number and Bagnold number.