(293d) Force-Based Prediction of the Segregation Velocity in Granular Mixtures

Predicting particle size-segregation in granular mixtures has remained challenging due to the lack of a general model for the segregation velocity that is applicable across a range of flow geometries, flow conditions, and particle sizes. In analogy to the classic fluid mechanics problem of the terminal velocity of a spherical particle in an otherwise quiescent viscous liquid, we consider the balance of the segregation force, drag force, and weight on a single intruder particle in a granular flow. Since the drag force depends on the intruder particle velocity relative to bed particles, this simple force balance allows the calculation of the segregation velocity. To extend this from a single intruder particle to particle mixtures, we exploit recent advances in particle-scale modelling of the segregation and drag forces and their dependence on local flow conditions over the entire particle species concentration range. Using discrete element method simulations, we show that this force-based approach correctly predicts particle segregation velocity in a diverse set of idealized and natural granular flow geometries for particle size ratios up to three. When incorporated in the well-established advection-diffusion-segregation continuum formulation, the force-based segregation velocity model has the potential to accurately capture size segregation phenomena in many relevant industrial applications. Supported by NSF Grant No. CBET-1929265.