Tuesday, 25 April 2006 - 8:00 AM

DEM modeling of hopper flows: comparison and validation of models and parameters

Rasmus Martin Hemph, Berend Van Wachem, and Alf-Erik Almstedt. Multiphase Flow Group, Applied mechanics, Chalmers University of Technology, Gothenburg, SE-41296, Sweden

In this paper, the influence of the various assumptions and simplifications employed in soft-sphere distinct element (DEM) simulations of particle processes is investigated. The impact of the various simplifications is shown on a simulation of a hopper and validated versus experimental data. In soft-sphere DEM simulations, the particle-particle interactions are modeled by the local deformation, using a spring-slider-dashpot concept. The determination of the parameters required in this mathematical framework and their sensitivity to the particle behavior is investigated. The dependency on the integration time step, fluid-particle interactions, dimensionality, and friction is also investigated. It is shown that the hopper particle simulations are fairly insensitive to the integration time step, the dimensionality, the fluid interactions and particle stiffness. The inclusion of frictional forces on the particles is however of major importance. The computational cost, efficiency, and the robustness of the various assumptions are shown. Finally a derivation for a suitable simulation time step is presented.

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