Multiscale modelling of dense gas–particle flows

In large-scale industrial processes involving granulation, coating, and production of base chemicals and polymers dense particulate flows with coupled mass, momentum, and heat transfer are frequently encountered. Both (effective) fluid–particle and (dissipative) particle–particle interactions need to be accounted for because the mutual competition between these phenomena govern the key features of dense gas–particle flows such as regime transitions. These interactions prevail at different length scales and consequently a multiscale approach is adopted to arrive at a quantitative description of these complex flows. In this approach detailed models, taking into account the relevant details of fluid–particle interaction (DNS) and particle–particle interaction (DEM) are used to obtain closure laws to feed two-fluid models (TFMs) which can be used to simulate the flow on a much larger (industrial) scale. In this chapter, we will discuss recent advances in the multiscale simulation of dense gas-fluidized beds. The governing equations will be presented as well as the key features of the numerical solution method. For each model type, illustrative computational results will be presented. Finally, areas which need substantial further attention will be discussed.