Solid-solid drag for continuum models using CFD-DEM simulations in gas fluidized beds of bidisperse mixtures

In fluidized beds, particles with a size distribution can usually be detected. The drag forces between particulate phases of different sizes could be as important as the gas-solid drag forces. Due to large number of particles present in fluidized beds, the models based on Eulerian viewpoint of phases are widely used for computer simulations. Such a viewpoint requires sufficiently fine grids to obtain accurate hydrodynamics, which is computationally costly. To facilitate coarse grid simulations, the effects of unresolved flow structures must be considered using the subgrid models. In this work, we computationally study bidisperse particle mixtures using the coupled Computational Fluid Dynamics (CFD) – Discrete Element Method (DEM) simulations in gas fluidized beds. Spatial averaging is performed to analyze the correction needed for a solid-solid drag model at different size ratios that will make the model suitable for coarse grid simulations. Different variables in the solid-solid drag model are analyzed and its dependence on the correction factor are presented. • CFD-DEM simulations studying bidisperse mixtures in a gas fluidized bed. • Importance of particle size ratio on fluidization behavior. • Spatial averaging to analyze correction factor for drag term in continuum model. • Assessment of different variables on the correction factor.