Granular temperature in a boundary-driven oscillating granular inclined flow

Abstract

An inclined granular flow on an ordered bottom presents complex behaviors. With a moderate inclination angle, a complete oscillation period contains a developing ordered flow, a sustained disordered flow, and two transitions: ordered–disordered (O–D) transition and disordered–ordered (D–O) transition, respectively. Unlike other granular systems, this ordered flow in our case is unstable and breaks down owing to a shear-induced explosion, where the velocity distribution vs depth develops from Newtonian type to Bagnold type. For the disordered flow case, a Bagnold-type bulk flow maintains above the “hot” basal layer. A detailed analysis shows that the O–D transition starts from a heating, which appears at the surface, and the disordering transports downwards to the basal layer with a granular temperature scaled by pressure T/P for local disordering. A shear-induced dilation in a basal layer produces an “explosion.” For the D–O transition, an ordering occurs in the basal layer with another scaled granular temperature T/P and then the ordering transports upward to the top surface.