Experimental study of two-dimensional, monodisperse, frictional-collisional granular flows down an inclined chute

In this study, positions, velocities, and rotations of monodisperse disks confined two-dimensionally in a glass-walled chute are measured using a high-speed camera. Steady, fully developed granular flows (SFD) down bumpy inclines are systematically investigated in the frictional-collisional (dense, rapid) regime. Three bottoms with different effective roughness heights and roughness distributions are studied to evaluate the influence of the bottom condition. The granular flows are shallow, having a typical depth of ten disk diameters. In the range of flow rates and inclination angles where SFD flows occur, the mean discharge velocity is approximately proportional to the flow depth. The surface solid fractions slightly decrease from the bottom to the free surface. The streamwise velocity profiles are close to the linear profile at small inclination angles, whereas at large inclination angles, they are best approximated by the Bagnold profile. The mean angular velocity is equal to the half shear rate everywhere in the flow except near the free surface and the bottom. At large inclination angles, relatively deep SFD flows exhibit an S-shaped granular temperature profile, but in the core, the temperature is far from scaling linearly with the square shear rate. The streamwise and crosswise translational temperatures are slightly different from each other, whereas the rotational temperature is only half of the crosswise translational temperature. The rough bottoms have complex influences on the granular flows as revealed by the velocity and temperature profiles. (c) 2006 American Institute of Physics.