Transient Computational Fluid Dynamics/Discrete Element Method Simulation of Gas-Solid Flow in a Spouted Bed and Its Validation by High-Speed Imaging Experiment

A coupled computational fluid dynamics (CFD)/discrete element method (DEM) is used to simulate the gas-solid two-phase flow in a laboratory-scale spouted fluidized bed. Transient experimental results in the spouted fluidized bed are obtained in a special test rig using the high-speed imaging technique. The computational domain of the quasi-three-dimensional (3D) spouted fluidized bed is simulated using the commercial CFD flow solver ANSYS-FLUENT. Hydrodynamic flow field is computed by solving the incompressible continuity and Navier-Stokes equations, while the motion of the solid particles is modeled by the Newtonian equations of motion. Thus, an Eulerian-Lagrangian approach is used to couple the hydrodynamics with the particle dynamics. The bed height, bubble shape, and static pressure are compared between the simulation and the experiment. At the initial stage of fluidization, the simulation results are in a very good agreement with the experimental results; the bed height and the bubble shape are almost identical. However, the bubble diameter and the height of the bed are slightly smaller than in the experimental measurements near the stage of bubble breakup. The simulation results with their experimental validation demonstrate that the CFD/DEM coupled method can be successfully used to simulate the transient gas-solid flow behavior in a fluidized bed which is not possible to simulate accurately using the granular approach of purely Euler simulation. This work should help in gaining deeper insight into the spouted fluidized bed behavior to determine best practices for further modeling and design of the industrial scale fluidized beds.