Dynamics of discrete wet granular avalanches in a rotary drum

The dynamic behavior of cohesive granular flows is important in geo-mechanics and industrial applications, yet poorly understood. We studied the effects of liquid viscosity and particle size on the dynamics of wet granular avalanches, occurring in a slowly rotating drum. A Discrete Element Method (DEM) model, in which contact forces and cohesive forces were considered, was employed to simulate this flow behavior. We found that the avalanche amplitude, flow layer velocity and granular temperature decrease as viscosity increases, but increase with particle size. Increasing the viscous forces causes the flow to behave as a bulk, pushing the free surface towards a convex shape, and avalanches become less pronounced. We found that this transition from avalanching flow to continuous flow can be characterized by evaluating the local fluctuations of the surface angle.