• discrete element method;
  • coarse grain model;
  • DEM–CFD method;
  • bubbling fluidized bed;
  • computational granular dynamics;
  • Geldart B


The discrete element method (DEM) is widely used in calculating powder systems. The DEM makes it possible to determine the complicated phenomena related to particle flowability. However, DEM has a fatal problem, which is that the number of calculated particles is restricted due to excessive calculation costs. Consequently, we have developed a large-scale model of the DEM, which is called the coarse grain model. The coarse grain particle represents a group of the original particles. Therefore, a large-scale DEM simulation can be performed using an extremely small number of the calculated particles. In our previous studies, the coarse grain model was applied in gas–solid and solid–liquid flow systems. It is anticipated that the coarse grain model will be used in various powder systems. In the current study, the coarse grain model has been applied to a two-dimensional bubbling fluidized bed. The adequacy of the coarse grain model was proved by a comparison with the original particle behavior. The simulation results obtained using the coarse grain model showed good agreement with the results for the original system. Moreover, the calculation speed with the coarse grain model was shown to be much faster than the calculation speed of the original model. Copyright © 2010 John Wiley & Sons, Ltd.