Experimental and computational studies of dense granular flow: Transition from quasi-static to intermediate regime in a Couette shear device

Rheology of dense granular material in an annular Couette cell is studied by experimentation and simulation. A transition from quasi-static to intermediate behavior is identified when a secondary vertical flow is induced. This secondary flow-induced transition and a power–law relation between stress and shear rate in the intermediate regime are verified to be robust rheological features by simulation using discrete element method (DEM). The insensitivity of this transition to certain particle and operational parameters is also shown by the simulation. The transitional and intermediate behavior is modeled by an order parameter (OP) based model with the fluidlike stress calculated using a constitutive relation from the kinetic theory for granular flows (KTGF). The suitability of this approach is discussed.