Modeling bulk solids behavior numerically with the Discrete Element Method (DEM) offers an
opportunity towards a better understanding of granular systems by studying local phenomena at
the particle level, which sometimes cannot be studied experimentally. The method could be used for
the prediction of e. g. flow behavior of materials with different properties or the course of a
mixing process at different process scales, eventually without the need of further experiments.
However, most research done with DEM simulations is limited to small-scale setups.
This work presents a study of bulk solid phenomena for cohesionless materials at larger equipment
scales by scaling up particle size in simulations, while implementing simplifications of the DEM model. These simplifications require calibration of the properties of the particles used in simulation to mimic the physical bulk behavior of the real materials.
Based on shear dominated applications, a calibration method for scaled particles using rolling friction is established with a focus on determining friction coefficients. This method consists of a combination of shear testers, a rotating drum experiment as well as a material tester. Based on
well-defined key parameters for comparison between numerical and laboratory experiments, a
calibration methodology is developed for essential material parameters to describe bulk solids
behavior, while simultaneously scaling up particle size. Quantitative limitations regarding
scale-up factors and validity limits for friction parameters and flow regimes of this methodology
are presented as well. Examples of successfully determined friction parameters are shown and
discussed for model particle systems with errors in bulk behavior in the range of 1 to 6% compared
with lab experiments. Further suggestions to complete and optimize the calibration method are
briefly discussed.
As a case study, a granular mixing experiment was set up for validation of calibrated DEM
simulations with scaled particles, using physical experiments of model mixtures. Based on two key
parameters for comparison - being mixing homogeneity in the course of the mixing event and the
required torque-on-shaft - effects of fill height, rotational speed, particle size scaling and
other parameters are presented. The effects and limitations of particle size scaling in simulation
to represent the real components on the key parameters are discussed for several
model mixtures.
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