Acceleration of CFD simulation of gas–solid flow by coupling macro-/meso-scale EMMS model

Gas–solid flow features significant dynamic multi-scale structure; multi-scale modeling is therefore in order. In this article, the macro-scale EMMS model was coupled with a two-fluid method (TFM) elaborated by the meso-scale EMMS model resolving sub-grid scale heterogeneity to simulate the hydrodynamics of circulating fluidized bed (CFB) risers. The overall flow distribution under the steady state was approximately predicted by the macro-scale EMMS model, which serves as the initial condition for meso-scale TFM simulations reproducing the dynamic behavior of heterogeneous gas–solid flows. Using the solid circulation flux as criterion, it was shown that this coupling approach can significantly reduce the time required to reach the statistically steady state, as compared to the packed bed or homogeneously dispersed initial condition. It also suggests a general approach to speedup dynamic simulation in the multi-scale paradigm of computation.