Comparison of different drag coefficient correlations in the CFD modelling of a Laboratory-Scale Rushton-Turbine Flotation Tank

Accurate specification of the drag coefficient, considering the influence of turbulence, is important in correctly predicting the air-water flow in a stirred tank. Multiphase CFD simulations in a laboratory-scale Rushton-turbine flotation tank were performed to explore the effects of four different drag coefficient correlations which were implemented in the CFD solver via user defined functions. An Eulerian-Eulerian multiphase approach with the dispersed k-e turbulence model was used to predict the gas holdup under turbulent and laminar flow conditions. Comparison of the gas holdup predictions obtained by different drag coefficient correlations showed that the choice of drag coefficient formulation significantly contributes to improving the accuracy of numerical predictions in each flow regime. The results also suggest that further improvement in the CFD simulation of stirred tanks can be achieved by better quantification of the turbulent properties associated with the interfacial forces between the continuous phase and the dispersed phase.