Computational fluid dynamics simulation of polydispersed bubbly flow in continuous casting mold: Investigations on bubble-induced turbulence effect

The dispersed bubbly flow dramatically changes the shear-induced turbulence (SIT) in gas–liquid systems. Modifications to the liquid turbulence model by adding source terms or a bubble-induced turbulence (BIT) viscosity term can improve the accuracy of numerical simulation. However, there is no consensus on the definition of the characteristic time scale of turbulent eddies induced by bubbles, which directly relates to the modeling work of the BIT source. We compared the effects of different character time scale models on multi-scale bubbly flow and developed a novel BIT model based on the gas-phase intrinsic turbulence parameters. Then, the coupling mechanism between SIT and BIT models was revealed. The results show that the population balance and Sato models show better consistency than other models for simulating bubble diameter and flow regimes. The bubble response time significantly underestimates the characteristic time, thereby enhancing the collision frequency between bubbles. A novel mixture BIT model is proposed based on the turbulent properties of gas and liquid phases. Compared with the numerical simulation of the without BIT model, the mean relative error predicted by the novel BIT is reduced by 45.28%. Finally, introducing the BIT viscosity model and the smallest eddy dissipation time model forms a positive feedback loop between BIT and liquid-phase SIT, thereby enhancing turbulent dispersion. However, an anomalous negative feedback loop mechanism was formed between BIT and SIT when using the bubble response time model.