Density-driven segregation of binary granular mixtures in a vertically vibrating drum: The role of filling fraction

This paper investigates the influence of filling fraction on the segregation patterns of binary granular mixtures in a vertically vibrating drum through experiments and simulations. Glass and stainless steel spherical grains, which differ in mass density, are used to give rise to density-driven segregation. The results reveal four segregation patterns, including Brazil nut effect segregation, counterclockwise two-eye-like segregation, dumpling-like segregation and clockwise two-eye-like segregation. The theoretical analysis demonstrates that grains predominantly exhibit counterclockwise convection at low filling fractions, while clockwise convection dominates at high filling fractions. Competition between buoyancy and convection forces determines the final stable segregation pattern. These findings provide valuable insights into controlling segregation in granular systems, which is crucial for optimizing industrial processes in fields such as pharmaceuticals and chemical engineering.