Influence of internal friction on transport properties in sheared granular flows

The effect has been studied of the internal friction coefficient of particles on transport properties of sheared granular flows. Experiments were performed in shear cell devices under four different internal friction coefficients of the particles and five different solid fractions. The motions of the granular materials were recorded by a high-speed camera. By using image processing technology and the particle tracking method, we measured and analyzed the distributions of the average velocity, fluctuation velocity, and particle self-diffiusion coefficient. Three bi-directional stress gages were used to measure the normal and shear stresses along the upper boundary. According to the experimental results, the stresses and the self-diffusion coefficients of the particles were inverse proportional to the internal friction coefficients. In the same conditions, the normal stresses were apparently higher than the shear stresses. The fluctuation and the self-diffusion coefficients in the streamwise direction were obviously higher than those in the transverse direction. The normal and shear stresses were found to increase with the solid fraction, but the diffusion coefficients were greater in a more dilute flow system. In addition, the deviations of self-diffusion coefficients in the low solid fraction condition were much greater than those in the high solid fraction condition. (c) 2006 American Institute of Chemical Engineers.