10-04-2017, 07:23 PM
The flow of granular materials is an important phenomena in a number of industrial processes, such as the transport of food-grains, ores, catalysts, powders, etc; as well as in many natural processes such as mud slides and avalanches. However, there is no single constitutive equation which can reproduce the diverse behavior observed in granular materials. The flow of granular materials is generally classified into three distinct flow regimes, where both continuum models and kinetic theory based models are used to predict the flow behavior. Experimental measurements of the profiles, distributions and correlations of flow parameters will help in developing and understanding the hydrodynamics in different flow regimes. In this presentation, measurements of particle statistics in the slow sheared flow of rice grains in a cylindrical couette will be discussed. The velocities of particles were obtained using video imaging and particle tracking at the free surface. Individual frames were analyzed using standard image analysis techniques to obtain instantaneous flow properties. Average flow profiles, such as the mean velocity and the mean spin, were obtained by dividing the flow zone into radial bins and averaging the relevant properties in each bin. Subsequently, velocity distributions and spatial and time correlations of fluctuations were calculated. Evidence of spatially correlated motion is presented. A rapidly decaying shear layer is observed, and the velocity distribution measured is non-gaussian and follows a power law behavior for large velocities. Evidence of cosserat type effects as predict by some continuum models is also discussed.