Two-Fluid Eulerian-Eulerian CFD Modelling of Bubbly Flows Using an Elliptic-Blending Reynolds Stress Turbulence Model

In Eulerian-Eulerian two-fluid computational fluid dynamic (CFD) predictions of bubbly flows, the lateral void fraction distribution mainly results from a balance between the lift and wall lubrication forces. The impact of turbulence modelling on the void fraction distribution has not, however, been examined in detail. In this paper, this impact is studied with an elliptic blending Reynolds stress turbulence model (EB-RSM) that resolves the near-wall region and includes the contribution of bubble-induced turbulence. Lift and wall lubrication forces are deliberately neglected. Comparisons against data on bubbly flows in a pipe and a square duct show that the EB-RSM reproduces the lateral void fraction distribution, including the peak in the near-wall region. The accuracy of this approach is comparable to best-practice high-Reynolds k-ε and second-moment turbulence closures that include lift and wall lubrication contributions. Overall, the role of the turbulence field is demonstrated to be significant in determining void fraction distributions, and has to be modelled appropriately if more accurate and consistent modelling of bubbly flows is to be achieved. In view of this, the present EB-RSM approach is useful as a starting point to develop a more accurate and generally applicable set of closure models for two-fluid CFD approaches.