A Multi-Scale Framework for CFD Modeling of Multi-Phase Complex Systems Based On the EMMS Approach

This talk elaborates a multi-scale framework for modeling of multi-phase complex systems from the perspective of the Energy-Minimization Multi-Scale (EMMS) approach. First, it is recognized that mass and momentum conservative equations are still inadequate to acquire a complete description of the multi-scale structures in multi-phase complex systems. The relationship between meso-scale structure parameters and meso-scale energy consumption, and the stability condition reflecting the compromise between different dominant mechanisms might be indispensable for each specific complex system. Second, when applied to a global multi-phase system, the EMMS approach could capture the jump change of macro-scale structure parameters, and supply a theoretical prediction of some intrinsic structure evolution and a physical interpretation on regime transitions in multi-phase systems. The intrinsic similarity between gas-solid fluidization and gas-liquid bubble column systems could therefore be explored. Third, when applied to computational cells of CFD models, the EMMS approach could be integrated into the averaged conservative equations of Eulerian-Eulerian models through a seamless or some simplified ways, e.g., extracting the constitutive laws of averaged drag coefficient. Since these constitutive laws may carry the information from meso-scales, this integration would dramatically improve the coarse grid simulation of multi-phase systems such as gas-solid fluidization and gas-liquid bubble columns, and hence has great potential in simulation of industrial-scale processes.