On segregation in bidisperse granular flows

Abstract

We consider a monodisperse dry granular material flowing down a rough inclined channel with downslope contracting sidewalls: theoretically and numerically. Utilising the depth-averaged shallow granular theory together with an empirical, but discrete particle simulations validated constitutive friction law, an extended novel one-dimensional (depth-and width-averaged) granular hydraulic theory is presented. For steady flows, besides describing the subcritical flow state, the one-dimensional model also predicts two other steady states, for a range of upstream prescribed flow conditions and channel openings. These states are supercritical flows with weak oblique shocks (smooth when widthaveraged) and flows with a steady jump in the contraction region. Both, super-and subcritical flow states were verified by numerically solving the depth-averaged two-dimensional shallow granular model. Despite the strong inhomogeneities in the linear contraction region, the one-and two-dimensional solutions (averaged across the channel) incomparably match well.