Suppression and emergence of granular segregation under cyclic shear

Phys Rev Lett. 2013 Aug 16;111(7):078001. doi: 10.1103/PhysRevLett.111.078001. Epub 2013 Aug 16.


While convective flows are implicated in many granular segregation processes, the associated particle-scale rearrangements are not well understood. A three-dimensional bidisperse mixture segregates under steady shear, but the cyclically driven system either remains mixed or segregates slowly. Individual grain motion shows no signs of particle-scale segregation dynamics that precede bulk segregation. Instead, we find that the transition from nonsegregating to segregating flow is accompanied by significantly less reversible particle trajectories and the emergence of a convective flow field.