Numerical modelling of bubbling flow dynamic behaviour in a bubble column

2D and 3D numerical simulations with two-fluid approach were conducted to investigate the gas-liquid flow dynamic behaviour in a rectangle bubble column. In the simulations, k-ε and RNG k-ε turbulent models, which account for the influence of the bubbles on liquid phase turbulence, were employed to study the effect of such models on predication of the dynamic behaviour of the bubble plume. In addition, the influence of different interfacial force closures such as drag, lift and added mass forces were also assessed. The simulation results indicated that for the 2D cases, the use of k-ε model could merely yield a steady flow pattern with one big liquid circulation, while the use of RNG k-ε model could produce a steady flow pattern, characterised by the appearance of three large vortices. However, all the 3D simulations have captured the plume meandering behaviour. The results showed that the value of the turbulence eddy viscosity predicted with 3D simulation was one order smaller than that with 2D simulation. Particularly, the meandering period of the bubble plume predicted by RNG k-ε model, was obviously smaller than that predicted using k-ε model in 3D simulations. The former gave the average turbulence eddy viscosity to be almost one third of that predicted by the latter. The assessment of the use of different interfacial force closures and their combinations showed that the lift force has a pronounced effect on the result of bubbly flow behaviour besides the drag force. It was found that the predicted meandering period was much greater than the experimental observations without the inclusion of the lift force, while the predicted period was consistent with the experimental result when the lift force was considered. Our simulations also revealed that the inclusion of the added mass force could notably improve the prediction results.