  Particle segregation in dense flowing size-disperse granular mixtures is
driven by gravity and shear, but predicting the associated segregation force
due to both effects has remained an unresolved challenge. Here, a model of the
combined gravity- and kinematics-induced segregation force on a single intruder
particle is integrated with a model of the concentration dependence of the
gravity-induced segregation force. The result is a general model of the net
particle segregation force in flowing size-bidisperse granular mixtures. Using
discrete element method simulations for comparison, the model correctly
predicts the segregation force for a variety of mixture concentrations and flow
conditions in both idealized and natural shear flows.
