Continuum modeling of flow and size-segregation in dense, bidisperse granular mixtures

Dense granular systems, consisting of particles of disparate sizes, segregate based on size during flow, resulting in complex, coupled segregation and flow patterns. In this talk, we study size-segregation in three dense granular flow configurations: (1) gravity-driven flow down a long vertical chute with rough parallel walls, (2) annular shear flow with rough inner and outer walls, and (3) planar shear flow with gravity. We perform two-dimensional discrete element method (DEM) simulations of flow of dense, bidisperse granular systems in all three configurations, while varying system parameters, such as the flow rate, flow configuration size, fraction of large/small grains, and grain-size ratio, and we study the effects of these parameters on the segregation dynamics. Our simulations inform continuum constitutive equations for both the size-segregation flux as well as the diffusion flux. When coupled with the nonlocal granular fluidity model - a nonlocal continuum model for dense granular flow - we show that both the flow field and segregation dynamics may be simultaneously captured using this closed, coupled, continuum system of equations.