Particle segregation in inclined high-speed granular flows

We report on the discovery, using numerical simulations, of a segregation pattern in high-speed granular flows, in which size segregation is primarily driven by two-dimensional granular temperature gradients, rather than by gravity. In contrast to slower flows on gentle slopes, in high-speed flows on steep slopes, large particles no longer accumulate in the upper layers of the flow, but are trapped in the interior. The strong temperature gradients that develop between the interior of the flow and the surrounding dilute periphery appear to govern the segregation mechanism. Interestingly, these new segregated flows run at a much faster speed than similar monodisperse flows. This opens up promising perspectives for transporting granular material with enhanced efficiency. Importantly, we show that the kinetic theory for dense, inclined flows of binary mixtures can provide a relevant theoretical framework to explain the segregation patterns observed in the numerical simulations.

Automated summary

We have discovered a segregation pattern in high-speed granular flows, where size segregation is driven by two-dimensional granular temperature gradients instead of gravity. In contrast to slower flows, large particles in high-speed flows on steep slopes are not accumulated in the upper layers but trapped in the interior due to strong temperature gradients. Interestingly, these segregated flows run at a much faster speed than similar monodisperse flows, indicating potential for enhanced efficiency in granular material transportation. Importantly, we have shown that the kinetic theory for dense, inclined flows of binary mixtures can explain the segregation patterns observed in numerical simulations.