Modelling of Bubbly Two-Phase Flows Using a Population Balance Approach

Air-water vertical upward bubbly flows are simulated by combining the S-γ population balance approach with an Eulerian-Eulerian two-fluid model in order to improve our ability to predict bubbly flows and the evolution of the bubble size distribution. Improved agreement with experimental profiles of bubble diameter is achieved with the addition of an optimized coalescence model. Satisfactory agreement is also found using a Reynolds stress turbulence formulation, whose superior predictive capability to describe the turbulence field might be essential for the simulation of more complex flow conditions than considered herein. Finally, the use of two bubble classes, accounting separately for small spherical and larger cap bubbles, seems sufficient to predict the whole range of bubble diameters up to the transition to a slug flow.