Flow characteristics and mechanical mechanism analysis in a dense sheared granular system

Flow characteristics and the mechanical theory of granular flows in dense sheared granular systems have yet to be fundamentally understood because of the complexities and discreteness of these systems. This study derives the appropriate equations and effects of mechanical parameters on fluctuation velocity, and investigates the solid volume fraction for a dense granular assembly sheared between two parallel plates. Theoretical results are verified via a discrete element method simulation. Thereafter, the mechanical mechanisms of the granular flows in this dense sheared granular system are investigated using this simulation method. Results show that the fluctuation velocity of granules at the boundaries is larger than that in the middle of the clearance, which is opposite the variation tendency of solid volume fraction. A change in the mechanical parameters can directly influence fluctuation velocity, thereby inducing the variation of the solid volume fraction. Moreover, studies on the mechanical mechanisms of granular flows indicate that inertial number has more significant effects on shear dilatancy, micro-contact structures, and coordination coefficient than contact stiffness coefficient. That is, shear dilatancy amplitude, strong force chains, and coordination coefficient decrease with the increased inertial number. [Display omitted] •Fluctuation velocity at the boundaries is larger than that in the middle clearance•Variation of fluctuation velocity is reverse to that of solid volume fraction•The inertial number (I) has a significant effect on this sheared granular system•Strong force chains and coordination coefficient decrease with the increased I•As I increases, granular collisions become active and granules become loose