For the achievement of efficient packing, minimizing the space of occupation and maximizing the strength of packing, it is important to understand the underlying mechanisms. The behavior of identical elongated cylindrical particles is studied via Discrete Element Method (DEM) simulations and complementary experiments. The effects of coefficient of friction, coefficient of restitution, drop height, fill height, packing method, deposition intensity, particle size to container size ratio, and the number of glued spheres forming the cylindrical particle, are explored. It is found that the packing density increases with coefficient of restitution; drop height and number of constituent spheres and decreases with coefficient of friction and Young’s modulus. The most efficient packing scheme is pouring particles over the whole cross-section although deposition intensity and wall effects also play a role in choosing the most efficient packing scheme. The present work also investigates the effect of liquid addition on the packing of mono-sized spheres and mono-sized elongated particles of fixed diameter and varying length. Also, the discharge and flow behavior of steel and plastic nonspherical particles with varying aspect ratio (both varying diameter with constant length and varying length with constant diameter) through hopper was explored experimentally and via DEM simulations. In addition, the effect of fill height and hopper angle on hopper discharge rate of non-spherical particles was determined. As the fill height increases, the mass discharge rate increases and then asymptotes; further increases in fill height cause a decrease in the mass discharge rate. It was found that increasing liquid contact decreases the mass discharge rate but this effect become small at higher liquid contents greater than 8%. Finally, experimental results are directly compared to predictions from DEM simulations. The results indicate that DEM simulations are fully capable of reproducing trends in the discharge rate that are well known experimentally. For example, the discharge rate decreases with an increase in aspect ratio and fairly varies with the outlet width raised to the 3/2 power as given by the modified Beverloo correlation. The proposed modified Beverloo correlation predicts discharge rate of elongated particles well and error is reported to be within 15%.
|Advisor:||Curtis, Jennifer Sinclair|
|School:||University of Florida|
|School Location:||United States -- Florida|
|Source:||DAI-B 79/01(E), Dissertation Abstracts International|
|Keywords:||Cylinders, Dem simulation, Hopper discharge, Non-spherical particles, Particle packing|
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