Multi-scale numerical simulation of fluidized beds: Model applicability assessment

In the past few decades, multi-scale numerical methods have been developed to model dense gas-solid flow in fluidized beds with different resolutions, accuracies, and efficiencies. However, changes in fluidized beds' simulations are still not elucidated: (i) the proper selection of the sub-models, parameters, and numerical resolution; (ii) the multivariate coupling of operating conditions, bed configurations, polydispersity, and additional forces. Accordingly, a state-of-the-art review is performed to assess the applicability of multi-scale numerical methods in predicting dense gas-solid flow in fluidized beds at specific fluidization regimes (e.g., bubbling fluidization region, fast fluidization regime), with a focus on the inter-particle collision models, inter-phase interaction models, collision parameters, and polydispersity effect. A mutual restriction exists between resolution and efficiency. Higher-resolution methods need more computational resources and thus are suitable for smaller-scale simulations to provide a database for closure development. Lower-resolution methods require fewer computational resources and thus underpin large-scale simulations to explore macro-scale phenomena. Model validations need to be further conducted under multiple flow conditions and comprehensive metrics (e.g., velocity profiles at different heights, bubbles, or cluster characteristics) for further improvement of the applicability of each numerical method.