A detailed gas-solid fluidized bed comparison study on CFD-DEM coarse-graining techniques

Computational Fluid Dynamics - Discrete Element Method (CFD-DEM) is a numerical tool used for detailed fluidized bed studies. However, CFD-DEM is computationally expensive, leading to a restriction regarding the number of simulated particles. Therefore, coarse-graining techniques have been developed to increase the simulation scale or reduce computational requirements for CFD-DEM simulations in fluidized beds. In this work, we critically compared the coarse-graining scaling laws of Mu et al. [2020, Chemical Engineering Science: X 6.] and Sakai and Koshizuka [2009, Chemical Engineering Science: 64, 533–539.] for their effectiveness in characterizing the original system. The first mentioned approach was not able to accurately characterize the original system, while the latter methodology showed good correspondence. We also demonstrated that applying a continuous two-way smoothing function to the coarse-graining process can yield grid-independent solutions, particularly when the particle diameter is much larger than the grid cell size, which is often the case in CFD-DEM simulations.