Title: Coupled continuum modeling of flow and size segregation in dense granular materials

Author (Talk): Harkirat Singh, Brown University

Abstract:

Dense, bidisperse granular mixtures segregate based on grain size during flow. The two primary driving forces of size segregation are pressure gradients and shear strain-rate gradients, which we study using three-dimensional discrete-element method (DEM) simulations of dense, bidisperse spheres. Based on the DEM simulations, we propose three-dimensional constitutive equations for the shear strain-rate gradient driven and pressure gradient driven fluxes. Upon coupling the segregation constitutive equations with the nonlocal granular fluidity (NGF) model (a nonlocal continuum model for dense granular flow), the coupled model is able to predict segregation dynamics and flow fields across different flow geometries. The coupled model shows good quantitative agreement with DEM simulations in several quasi-one-dimensional flows, including vertical chute flow, inclined plane flow, planar shear with gravity flow, and anti-plane shear flow. Moreover, it captures the salient features of segregation dynamics in several complex flow configurations, namely annular shear flow with gravity, heap flow, and split bottom flow