A turbulence model for large interfaces in high Reynolds two-phase CFD

• Two-phase CFD commonly involves interfaces much larger than the computational cells.
• A two-phase turbulence model is developed to better take them into account.
• It solves k–epsilon transport equations in each phase.
• The special treatments and transfer terms at large interfaces are described.
• Validation cases are presented.

A model for two-phase (six-equation) CFD modelling of turbulence is presented, for the regions of the flow where the liquid–gas interface takes place on length scales which are much larger than the typical computational cell size. In the other regions of the flow, the liquid or gas volume fractions range from 0 to 1. Heat and mass transfer, compressibility of the fluids, are included in the system, which is used at high Reynolds numbers in large scale industrial calculations. In this context, a model based on k and ɛ transport equations in each phase was chosen. The paper describes the model, with a focus on the large interfaces, which require special treatments and transfer terms between the phases, including some approaches inspired from wall functions. The validation of the model is based on high Reynolds number experiments with turbulent quantities measurements of a liquid jet impinging a free surface and an air water stratified flow. A steam–water stratified condensing flow experiment is also used for an indirect validation in the case of heat and mass transfer.