(412c) Continuum Modeling of Density Segregation for Bidisperse Granular Materials

Preventing spontaneous segregation of flowing granular mixtures is an ongoing challenge for many industrial processes that involve the handling of bulk solids. Recently, a continuum-based modeling approach has been developed that accurately predicts spatial concentration fields in a variety of flow geometries for mixtures varying in size.  The transport equation based approach considers the interplay between advection, diffusion, and segregation using kinematic information obtained from experiments and/or discrete element method (DEM) simulations combined with an empirically determined relation for the segregation. In this research, we extend the domain of the model to include density driven segregation. DEM simulations of density bidisperse flows of mono-sized particles in a quasi-2D bounded heap were performed to determine the dependence of the density driven segregation velocity on local shear rate and particle concentration. Using this relation, which is similar to that for size bidisperse mixtures, in the model yields theoretical predictions of segregation patterns that quantitatively match the DEM simulations over a range of density ratios and flow rates. Corresponding experiments were performed that reproduced the segregation patterns obtained in both the simulations and the theory, indicating that the theory is able to capture the physics of density driven segregation in granular heap flow.