Impact of granular segregation on the solid residence time and active-passive exchange in a rotating drum

Segregation behavior of binary mixtures of cylindrical particles with different length ratios in the rotating drum

“…In particular, a threshold of greater than 0.1 s is adopted to limit the influence of the frequent crossing of the particles between the active and passive interface, which is especially the case for the small particles in the radial core region. It should be noted that the SRT is averaged over the time period of 50–200 s, that is, at pseudo‐staeady state after the completion of fast radial segregation (Figure ), because the SRT varies little during the slow axial segregation, which agrees with that for binary mixtures of spherical particles . Figure presents the histogram of the SRT values of the large and small cylindrical particles with a length ratio of 2 in the active and passive regions of the rotating drum.…”

“…The decreasing exchanging rate of the large species is because of the progressive movement toward the radial periphery of the drum, while the increasing exchanging rate of the small species is due to the progressive movement toward the radial center, after which the rate of each particle species fluctuates around a constant value. This tendency of the binary mixtures of cylindrical particles is similar to that of spherical ones . Enlarging the length ratio obviously decreases and increases the exchanging rate of large and small cylindrical particles, respectively, which is attributed to the enhanced segregation extent between the two particle species (Figure ).…”

“…Figure presents the histogram of the SRT values of the large and small cylindrical particles with a length ratio of 2 in the active and passive regions of the rotating drum. Similar to the SRT distribution of the binary mixtures of spherical particles, the SRT histograms in the active and passive regions are distinctly different in terms of both SRT magnitudes and shapes of histograms, demonstrating the significant effect of the fast radial segregation on the SRT characteristics of different cylindrical particles. In the active region (Figure a,c), the histograms are approximately Gaussian for both large and small cylinders, but the latter exhibit a wider range of SRT values, particularly with a significant proportion of lower SRT values (<0.4 s) due to the preferential segregation of the small particles to the radial core.…”

“…As the length ratio increases, the SRT values (a) decrease for both constituents in the active region, which is due to the steeper bed surface giving higher potential energies (Figure ); and (b) increases for the large constituent in the passive region due to the more extensive radial segregation, but remains unchanged for the small constituents in the passive region (Figure ). As compared with the mean SRT of the binary mixtures of spherical particles, the mean SRT of the large and small cylindrical particles in the active region of around 0.50 and 0.53 s are 30–40% smaller than the corresponding spherical particles . The reduction in the SRT of both constituents can be attributed to the steeper bed surface of the cylindrical particles.…”

Discrete Element Method Simulation and Experimental Validation of Pattern Development in a Rotating Drum Mixer

“…Segregation processes in a horizontal tumbler were also studied numerically. Yang et al studied the segregation of a binary‐sized mixture of glass spherical particles in a horizontal rotating drum by using discrete element method (DEM) simulations with very similar dimensions to those presented in this paper. They identified dynamically dead volumes and discussed the influence of the size of these non‐active regions on global mixing characteristics, such as mixing indexes, the gyration radius, and kinetic energy.…”