Modeling and validation of coarse-grained computational fluid dynamics-discrete element method for dense gas-solid flow simulation in a bubbling fluidized bed

Computational fluid dynamics (CFD) combined with the discrete element method (DEM) are powerful tools for analyzing dense gas-solid flows. However, the computational cost of CFD-DEM will be unfeasibly great when simulating large-scale engineering applications with billions of particles. Accordingly, the coarse-grained (CG) CFD-DEM method is applied to solve this problem. This investigated method replaces several smaller particles with larger ones called parcels, aiming to reduce the number of particles and fully consider the collision of particles between composition parcels and the collision of particles within composition parcels. First, high-speed photography verifies the numerical simulation's reliability. Then, the CG CFD-DEM was used to analyze the transient spatial distribution, transient average velocity, pressure drop, bed height, and the mixing state of particles in a dense gas-solid fluidized bed. The CG CFD-DEM was also compared with the CFD-DEM results, which showed a good agreement with the calculation results and proved the accuracy and applicability of the method. Finally, the computation time of the CG CFD-DEM was evaluated, showing a significant decrease in computation time with an increasing coarse ratio (k). This investigation can provide theoretical reference for the numerical simulation of the CG CFD-DEM method in dense gas-solid flow.