Computer Simulation of Powder and Particle Flow using Micro-Dynamics Approach and Validation

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Powder and particle flows have been regarded as very complex phenomena. Research of those flows have been largely dependent on empirical approaches. Most of computer simulation of the powder and particle flows are based on continuum models. However, increasing computer power has made discrete particle simulation a practical means for predicting particle motion in various cases. The present project has been planned with two purposes ; (1) to develop the discrete particle simulation so that not only qualitatively but quantitatively good agreement should be obtained with experiments, (2) to develop three dimensional simulation model for practical use. To access simulation models, experiments were made using a high speed video camera and data processing facilities. Simulation results were compared with measurements. Based on the comparison, models were developed further to get quantitative agreement with experiments. A nonspherical particle model is an example which was deduced from the the above comparison. In the present project, attention was given to cohesion forces due to static electricity. Also, simulation was made of gas-solid flows where particles are dispersed in vertical duct. It was clarified in this work that formation of particle clusters observed in circulating fluidized beds can be explained by considering repeated collision of particles.Before proceeding the research to the 2nd purpose, comparison was made between 2-and 3-dimensional simulations. In the present project, a method of quasi 3-D simulation was proposed newly. The solid motion is obtained by 3-D calculation, while the gas phase is obtained by axisymmetric 2-D calculation. This quasi 3-D simulation was found to be a useful means to predict phenomena in spouted beds and bubbling fluidized beds of axisymmetrical vessel.