Simulations and physical measurements of glass spheres flowing down a bumpy incline

An inclined chute facility and its associated diagnostics has been developed and utilized to study the flow of granular materials. A variety of flow regimes and flow phenomena were observed. Fully developed flows were observed over a bumpy base for a range of slopes. Under some conditions, these flows were dominated by friction and under other conditions, collisions played a dominant role. A variety of unsteady flows were also observed. These include decelerating flows, accelerating flows, and wavy (periodic) flows. The characteristics of the base strongly influenced the flow regime and flow dynamics. Discrete particle simulation model parameters were determined from individual particle tests and particle impact experiments. Simulations of nominally steady flows at two fixed angles showed relatively good agreement with experimental values for particle velocities near the side-walls and on the top surface. The mass flow rate and the flow depth were also consistent with the experiments; however, both experiments and simulations exhibited significant fluctuations about the nominal mean values. The simulations were utilized to interpret flow parameters interior to the flow (i.e., in regions that cannot easily be measured non-intrusively). Far from the side-walls, the granular temperature was found to have a maximum near the bumpy base and to decrease toward the top surface - consistent with granular kinetic theory predictions for flows on bumpy inclines, without side-walls. Near the side-walls the behavior was substantially different with granular temperature decreasing from the top to a minimum at the lower 'corners' of the chute. This behavior is consistent with experimental measurements of fluctuation velocities near the side-walls. The simulations confirm that the previous discrepancy in the variation of the granular temperature with depth between kinetic theory and near-side-wall measurements was a result of the side-walls, which cause strong three-dimensional structure in the flow. (C) 2000 Elsevier Science S.A. All rights reserved.