Multiphase mixture model applied to cyclone separators and bubble columns

摘要

A large number of flows encountered in nature and industrial processes consist of a mixture of phases. Depending on the strength of the interaction between phases, different modeling approaches have been proposed for multiphase flows. Mixture models, with an intermediate complexity formulation, are well suited for problems involving dilute suspensions of solids or bubbly flows. This paper reports the implementation of a mixture model in the unstructured FLUENT code. The different phases are treated mathematically as interpenetrating continua with a volume fraction associated to each phase. The continuity and momentum equations are applied to the mixture, and an individual continuity equation is used to solve for the volume fraction of each phase. The main characteristic of this mixture model is that the relative velocities between phases are obtained from algebraic equations assuming local equibrium over short length scales. This mixture model has been applied to complex industrial applications such as bubble columns and cylone separators, and a very satisfactory agreement has been achieved for the continuous and the dispersed phase, with the advantage of a reduced computational cost when compared with full multiphase models. Although further extensions of this model may be needed, it has been proven as an efficient tool for these applications.