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The packing of particles with a log-normal size distribution is studied by means of the discrete element method. The packing structures are analyzed in terms of the topological properties such as the number of faces per radical polyhedron and the number of edges per face, and the metric properties such as the perimeter and area per face and the perimeter, area, and volume per radical polyhedron, obtained from the radical tessellation. The effect of the geometric standard deviation in the log-normal distribution on these properties is quantified. It is shown that when the size distribution gets wider, the packing becomes denser; thus the radical tessellation of a particle has decreased topological and metric properties. The quantitative relationships obtained should be useful in the modeling and analysis of structural properties such as effective thermal conductivity and permeability. [ABSTRACT FROM AUTHOR]

Thispaper presents a numerical study of particle flow and sieving behavioron a vibrating screen. The particle flow is modeled by means of discreteelement method (DEM) at a particle scale. The DEM model is first verifiedby the good agreement between the numerical and experimental resultsin terms of the distribution of percentage passing of different sizedparticles along the screen deck. The effects of variables such asincline angle, vibrating frequency, and amplitude are then studiedwith special reference to the overall screen efficiency and distributionof the passing rates for different sized particles. The performanceof such a screening process is shown to be related to particle flowon the screen such as the structure of particle bed, particle velocities,and particle–particle and particle–deck interactions.In particular, it is demonstrated that the sieving performance atthe process equipment scale can be linked with the particle–deckcollisions obtained from the DEM simulations, facilitated by the well-establishedprobability theory. Finally, based on the simulation data, a mathematicalmodel is proposed to link the particle–deck collisions withthe three variables considered. The mathematical model can satisfactorilyestimate the process performance in terms of weight percentage passings,particularly when the effect of particle–particle interactionsis not significant. [ABSTRACT FROM AUTHOR]

Coordination number is an important microscopic parameter in describing the packing of particles. However, little information is available for particle mixtures because of the difficulty of investigating them experimentally. This article presents a numerical study on the coordination numbers of a ternary packing system with size ratios of 24.4/11.6/6.4 by means of the discrete element method (DEM). Good agreement between the simulated and measured results was obtained, which confirms, at a particle scale, that DEM is capable of generating reliable results for structural analysis of particle packing. It was also found that the coordination number distribution of each of the cases considered can be described by the so-called Johnson SBfunction. The distribution parameters of the function were quantified based on the DEM simulation results so that the coordination number distributions corresponding to different contact types in this ternary packing system can be fully described. [ABSTRACT FROM AUTHOR]