LAUSR

Abstract This work presents a novel method to quantitatively characterize and investigate the transient local segregation behavior of the binary (3 and 6 mm) particles inside a wedge-shaped hopper during the discharge process. The space in which binary particles existed is first mapped by the 10 mm × 10 mm square grids. Based on the data obtained by discrete element method (DEM) simulation, the ratios of the transient mass fraction of 3 mm particles in the mixture to the original fraction are calculated and then clarified into the seriously positive (++), positive (+), well-mixed (0), negative (−), and seriously negative (−−) levels, respectively. The relationships between the fraction of each segregation index (SI for short) and the flowing time are quantitatively analyzed in the center, middle, and edge regions. The local segregation begins to change when the flowing time reaches 1000 ms, which is about half of the total discharge time. Along with the formation of a ‘V’ shape funnel flow, the large-sized particles prefer to roll toward the center of the hopper, thereby leading to negative segregation, and both the fractions of SI(−) and SI(−−) increase by as high as 0.6 and 0.3, respectively. Under the present simulation conditions, the factors of the initial mass ratio of the large size particle to the small one, and the particle density, directly and obviously affect the transient local segregation behavior, and the fraction of SI(−−) in the center region is increased by at least 0.4. The particle size difference mainly affects the segregation behavior in the edge region at a limited degree, specifically when the particle size difference increases by 1 mm, the fraction of SI(0), which is used to determine the uniform degree of the mixture, is reduced by about 0.1. In addition, the influences of both the friction coefficient among the particles and that between the particles and the wall on the segregation behavior during the discharge process can be negligible in comparison with other factors.