EMMS-based multi-scale CFD

The EMMS model was proposed for the time-mean behavior of fluidized beds on the reactor scale. A more extensive application of the EMMS model to gas-solid flow is through its coupling with the two-fluid CFD approaches, which brings about an EMMS-based multi-scale CFD framework for gas—solid flow. For this purpose, Yang et al. (2003) introduced an acceleration, a, into the EMMS model to account for the... 

In fact, extremum tendencies expressing the dominant mechanisms in systems like turbulent pipe flow (Li et al, 1999), gas-liquid-solid flow (Liu et al, 2001), granular flow, emulsions, foam drainages, and multiphase micro-/nanoflows also follow similar scenarios of compromising as in gas-solid and gas-liquid systems (Ge et al., 2007), and therefore, stability conditions established on this basis also lead to reasonable descriptions of the meso-scale structures in these systems. We believe that such an EMMS-based methodology accords with the structure of the problems being solved, and hence realize the similarity of the structures between the physical model and the problems. That is the fundamental reason why the EMMS-based multi-scale CFD improves the... 

In this section we will present some examples of using the EMMS-based multi-scale CFD to solve industrial problems, including fluid catalytic cracking (FCC) and CFB combustion. 

In what follows we will give an example of using the EMMS-based multi-scale CFD to study the complex hydrodynamics and reactions in an industrial 150 MWe CFB boiler, which was designed by Harbin Boiler Co. Ltd. and installed in Guangdong, China. The hydrodynamics part has been reported (Wang and Li, 2010 Zhang et al., 2010) and the reactive part is referred to more recent work of Zhang (2010). 

Limited to computing capability, the following analysis confines the DNS to the fine-grid TFM simulation, which offers meso-scale closures for the correlative, coarse-grid TFM simulations. For comparison, the variational type of multi-scale CFD takes the EMMS-based models to close TFM simulations. 

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