EMMS-based discrete particle method (EMMS-DPM) for simulation of gas-solid flows

Understanding the hydrodynamics of gas-solid flows is a grand challenge in mechanical and chemical engineering. The continuum-based two-fluid models (TFM) are currently not accurate enough to describe the multi-scale heterogeneity, while the discrete particle method (DPM) following the trajectory of each particle is computationally infeasible for industrial systems. Following our previous work, we report in this article a coarse-grained DPM considering the meso-scale structure based on the energy-minimization multi-scale (EMMS) model, which can be orders of magnitude faster than the traditional DPM and can take full advantage of CPU-CPU (graphics processing unit) hybrid super-computing. The size and solids concentration of the coarse-grained particles (CGP), as well as their interactions with the gas Row (the drag) are determined by the EMMS model with a two-phase decomposition. The interactions between CGPs are determined according to the kinetic theory of granular flows (KTGF). The method is tested by simulating the onset of fluidization and the steady state flow in lab-scale circulating fluidized bed (CFB) risers with different geometries and operating conditions both in 2D and 3D. The results agree well with experiments and traditional DPM based on single particles. The prospect of this method as a higher-resolution alternative to TEM for engineering applications and even for virtual process engineering is discussed finally. (C) 2014 Elsevier Ltd. All rights reserved