Axial segregation of a binary mixture in a rotating tumbler with non-spherical particles: Experiments and DEM model validation

Segregation patterns in rotating cylinders determined by the size difference, density ratio, and cylinder diameter

Granular materials often segregate under mechanical agitation, which differs from the expectation of mixing. It is well known that a bidisperse mixture of granular materials in a partially filled rotating cylinder exhibits alternating bands depending on the combination of the two species. The dynamic angle of repose, which is the angle that a steady avalanche makes with the horizontal, has been considered the dominant parameter that determines the segregated state. However, the previously known angle of repose condition was not always satisfied in different experimental cases. To clarify the experimental conditions, we conducted an exhaustive parameter search with three dimensionless parameters: the particle size difference normalized by the average particle size, the specific density ratio, and the ratio of the cylinder diameter to the average particle size. Additional experiments were conducted to explore the effect of the rotational speed of the cylinder. This systematic approach enabled us to predict the segregated state. Moreover, we discovered that the band width can be effectively scaled by combining these three parameters.

Computer Aided Modeling of Wood Chips Transport by Means of a Belt Conveyor with Use of Discrete Element Method

The effectiveness and precision of transporting wood chips on the transport trailer or hopper depends on an inclination angle, a conveyor belt speed, and length. In order to devise a methodology aiding designing and the selection of technical and performance parameters (aiding the settings of conveyor belt sub-assemblies), the authors carried out the simulation tests concerning wood chips transport on the belt conveyor and their outlet. For the purposes of these tests, a simulation model was performed in the Rocky DEM (discrete element method) software in the numerical analysis environment and compared to analytical tests. The tested wood chips were taken from cherry plum branches chipping processes (Prunus cerasifera Ehrh. Beitr. Naturk. 4:17. 1789 (Gartenkalender 4:189-204. 1784)), out of which seven basic fractions were separated, which differed mainly in terms of their diameter from 5 mm to 50 mm and the length of 150 mm. The article presents the results of wood chips ejection distance in the form of the 3D functions of wood chips ejection distance depending on the conveyor belt inclination angle and belt speed. The results are presented for five conveyor belt lengths (1 m, 2 m, 3 m, 4 m, 5 m). The tests also involved the conveyor belt inclination angle in the range from 10° to 50° and the belt velocity in the range from 1 m/s2 to 5 m/s2. The numerical test results demonstrate higher average values of wood chips ejection distance than designated in the analytical model. The average arithmetical difference in the results between the numerical and analytical model is at the level of 13%.