Segregation of granular binary mixtures with large particle size ratios during hopper discharging process

Particle mixtures with a wide range of sizes, shapes, and densities may experience significant segregation. In the hopper discharging process, segregation predominantly happens on the free surface of mixtures with size ratio <5.0. However, when size ratio is much larger, the segregation developed is still not fully understood. Hence, this work aims to investigate the segregation of granular materials with large size ratios ranging from 4 to 14.3 during a conical hopper discharging process. The results show that small particles are fully discharged first, then large particles. The velocity difference between two kinds of particles at various locations are recorded and the results show that it is closely related to porosity, force structure and the number of free drop small particles. The effect of size ratio is examined, showing that mixtures with large porosity encounter serious percolation and smaller particles tend to be fully discharged quickly. For different hopper geometries, small particles fully discharged time is similar for small cone angles of 30° and 60° due to similar flow patterns; but for large cone angles of 120° and 180°, small particles are not fully discharged due to their accumulation on the sidewall.