Effect of particle density on the segregation of binary granular systems in a rotating drum
颗粒密度对旋转筒内二元颗粒体系分离的影响

The effects of particle density on the segregation of binary granular systems in a rotating drum are studied by the molecular dynamics simulation. The results show that the Brazil nut effect happens when the density of small granules is larger, whereas as the density of big granule increases, the segregation pattern is reversed and the reverse Brazil nut effect occurs. We also calculate the quantitative relationship between the segregation index and the density ratio. Finally, the mechanism of competition between percolation and condensation from Hong's theory is used to explain theoretically the reversion of segregation pattern.