(428b) Effect of Interfacial Forces on Mixing and Dispersion of Bubbles in Pipe Flows

Modelling the polydispersity features, e.g. size distribution, of the disperse phase is one of the crucial aspects of multiphase mixing simulations. Knowledge of the properties of the disperse phase is essential for accurate estimation of the interfacial heat and mass transfer occurring in practical and industrial mixing applications. In this regard, the population balance model coupled with the computational fluid dynamics, namely CFD-PBM, is a powerful tool for studying the evolution of the properties of the disperse phase and its interactions with the continuous phase.

Concerning the CFD, adopting the Eulerian-Eulerian framework, called Two-fluid model, is currently the only viable choice if the simulation target is the industrial-scale equipment. However, the performance of the two-fluid model depends strongly on the relations required to close the averaged field equations. The closure relations relevant to the momentum balance equation are termed as interfacial forces including mainly drag, lift, turbulent dispersion and wall lubrication forces. However, these models were mostly developed through simplistic theoretical/experimental methods that limits their applicability. Among the mentioned forces, lift and wall lubrication forces have been provoking ongoing debate over their physical explanation and corresponding suggested models.

In this work, the performance of two recent combinations of models proposed for the lift and wall lubrication forces are compared with each other using mono-disperse approach in a bubbly air/water two-phase system. Moreover, the potential for improving the results through adjustment of the lift coefficient is demonstrated. In the second part, the evolution of the bubble size distribution (BSD) is evaluated by employing the PBM method coupled with the Two-fluid model using the best setting for the interfacial forces. Eventually the results are compared with experimental data available.