Designing minimally segregating granular mixtures for gravity-driven surface flows

In dense flowing bidisperse particle mixtures varying in size or density alone, smaller particles sink (percolation-driven) and lighter particles rise (buoyancy-driven). But when particle species differ from each other in both size and density, percolation and buoyancy can either enhance (large/light and small/heavy) or oppose (large/heavy and small/light) each other. In the latter case, a local equilibrium can exist in which the two mechanisms balance and particles remain mixed: this allows the design of minimally segregating mixtures by specifying particle size ratio, density ratio, and mixture concentration. Using DEM simulations, we show that mixtures specified by the design methodology remain relatively well-mixed in heap and tumbler flows. Furthermore, minimally segregating mixtures prepared in a fully segregated state in a tumbler mix over time and eventually reach a nearly uniform concentration. Tumbler experiments with large steel and small glass particles validate the DEM simulations and the potential for designing minimally segregating mixtures.

Automated summary

In bidisperse particle mixtures with varying size or density, smaller particles sink and lighter particles rise. However, when particles differ in both size and density, percolation and buoyancy can either enhance or oppose each other. By specifying particle size ratio, density ratio, and mixture concentration, minimally segregating mixtures can be designed. DEM simulations and tumbler experiments with steel and glass particles validate the potential for designing such mixtures.