Influence of the drag coefficient of a single bubble in vertical upward turbulent bubbly flows

Abstract

Numerical simulations of upward turbulent bubbly flows in vertical pipes are carried out in the Euler-Euler framework with a low-Reynolds-number (LRN) model for liquid for various flow conditions. It is found that the correlation for the drag coefficient of a single bubble in a shear flow, which has been successfully used in numerical simulations with the high-Reynolds-number (HRN) models, cannot be used with the LRN model. The reason is an excessive value of drag coefficient of a single bubble in the near-wall cells. Therefore, a new correlation for the drag coefficient of a single bubble in shear flow has been proposed. The results of numerical simulations are analysed and compared to selected experiment results. It is shown that the largest effect of the application of the new correlation for the drag coefficient of a single bubble in shear flow can be achieved on the reduction of the relative velocity between gas and liquid. Overall, the results of numerical simulations agree well with the experimental results.