Verification and validation of a coarse grain model of the DEM in a bubbling fluidized bed

Dense granular flows are encountered in various engineering fields. The discrete element method (DEM) is used extensively for the numerical simulation of these flow types. Improvements in computer specifications have made it possible to apply the DEM in various systems. Although the DEM is well-established, it has a fatal problem. The problem is that the number of calculated particles is substantially restricted when the simulation needs to be finished within practical time using a single personal computer. On the other hand, many industries require application of the DEM to large scale systems on a single personal computer. We therefore developed the DEM coarse grain model in our previous studies. In the coarse grain model, a group of original particles is simulated using a large-sized particle termed a coarse grain particle, where the total energy is modeled to agree between the coarse grain and original particles. The coarse grain model therefore makes it feasible to perform large scale DEM simulations by using a smaller number of particles than the actual number. The coarse grain model thus far has been verified in two-dimensional fluidized beds. In this study, adequacy of the coarse grain model is verified and validated in a three-dimensional fluidized bed, where scaling ratio is low and high respectively. Consequently, the coarse grain model is shown to simulate the macroscopic behavior of solid particles in three-dimensional dense gas-solid flows. (C) 2014 Elsevier B.V. All rights reserved.