Resonance-induced acceleration of the RBNE-BNE segregation inversion

The experimental and simulation results indicate that the reverse Brazil nut effect (RBNE)-Brazil nut effect (BNE) segregation inversion happens faster in the circular-bottom container than that in the flat-bottom container. The starting location of the sinkage of heavier grains at the top layer is triggered with certain randomness in the latter, whereas it first occurs at either of the lateral edges of the bottom in the former. The occurrence of standing-wave resonant spots of higher and lower granular temperature accelerates the RBNE-BNE transition. From the elastic collision model of single grain, the bottom with a larger angle leads to more energy transfer from the vertical direction. The simulation results of a monodisperse granular bed confirm that the circular-bottom container possesses a higher granular temperature and a lower packing density at the lateral edges of the circular bottom, whereas the flat-bottom container has a uniform distribution with a standing-wave period.