Numerical modelling of bubble column reactors is a way of predicting the multiphase flow to improve the reactor design and understand the reactor fluid dynamics. The recent increase in interest in Computational Fluid Dynamics (CFD) spurred substantial research efforts in determining numerical models that can obtain reasonably accurate predictions with limited computational time, thus overcoming the limitations of traditional empirical methods.
When a dispersed flow is considered, two main models have been developed to predict the complex fluid dynamics phenomena: the Eulerian-Lagrangian and the Eulerian-Eulerian Multi-Fluid models. The Eulerian-Lagrangian model couples the Eulerian description of the continuous phase with a Lagrangian scheme for tracking the individual particulates. The dynamic of the surrounding fluid (continuous phase) is solved through the governing equations, while the particulates (dispersed phase) are tracked independently through the surrounding fluid by computing their trajectory. The interactions between the phases and their impact on both the continuous and the discrete phases can be considered, but it requires a greater computational effort. Consequently, it can not be used to simulate bubble columns at the industrial scale.
The Eulerian-Eulerian model considers each phase as interpenetrating continua. All the phases share a single pressure field, whereas continuity and momentum equations are solved for each phase. The coupling between the phases is achieved considering interfacial source terms.