Application of a novel model for bubble-induced turbulence to bubbly flows in containers and vertical pipes. (20th July 2019) - Liao, Yixiang
Highlights: A baseline closure concept is applied for model development and validation. The baseline model is updated regarding bubble-induced turbulence. The improvement is demonstrated for a wide range of bubbly flow conditions. Two-equation RANS model with additional BIT source terms was shown to be effective. Abstract: The baseline model for the CFD-simulation of turbulent bubbly flows in the Euler-Euler framework was proposed several years ago. It defines a fixed set of closures including all constants to avoid case by case tuning and to have a basis for sustainable model development. The present paper extends the baseline model by improving the modelling of bubble-induced turbulence. The closure terms in the transport equations of the k-ω SST model are revisited and replaced with the model recently proposed by Ma et al. (Ma et al., 2017. Physical Review Fluids 2, 034301) which is based on an analysis of the turbulent kinetic energy budget obtained from direct numerical simulation data. Detailed validation results for various flow configurations with a wide range of gas and liquid volumetric fluxes are presented. In case of vertical pipe flow significant improvements in the predicted gas volume fraction and velocity profiles are obtained, especially in high gas volume fraction cases where bubble-induced turbulence is dominant. Simulations of other configurations, such as uniform and non-uniform bubble columns, show that the model of Ma et al. (2017) results in an also for these cases overall improvement. Therefore, the baseline model is now updated to include the new model for bubble-induced turbulence.