A Modified Bubble Breakage and Coalescence Model Accounting the Effect of Bubble-Induced Turbulence for CFD-PBM Modelling of Bubble Column Bubbly Flows

Abstract

The behaviours of bubble-induced turbulence (BIT) have been demonstrated to be different from the homogeneous isotropic single-phase turbulence on the turbulence energy spectrum. The description of bubble/eddy-bubble collision to cause bubble coalescence and breakage are usually based on the classical Kolmogorov − 5/3 scaling law for the inertial subrange of the turbulence energy spectrum function. This approximation may no longer be appropriate for modelling the gas–liquid flow in the bubble columns as a large amount of turbulence eddies is generated by the BIT. Therefore, the present work focuses on the influence of κ−3 scaling of the BIT energy spectrum on the bubble coalescence due to bubble–bubble collision under turbulence and the breakage due to the eddy-bubble collision in bubble columns. A modified bubble coalescence and breakage model accounting for the BIT is proposed. The proposed coalescence and breakage model considers the mean turbulent velocity of eddies under the influence of bubble-induced turbulence and the characteristic wavenumber/length scale that corresponds to the BIT. A comparison of the simulation results with the experimental data clearly demonstrates that the modified bubble coalescence and breakage model appropriately describes the bubble coalescence and breakage events occurring under the influence of BIT in bubble columns.