Euler–Euler simulation of multi-regime two-phase flows with thin liquid films

In Euler–Euler simulations, the information on the interfacial structure of two-phase flow is lost due to the underlying phase averaging. Suitable interaction force models, which rely on assumptions about the local interfacial structure, are required to close the two-fluid model equations. Recent advances have produced multi-regime closure models, which allow simulations of continuous-dispersed and separated flows within the same domain. Here, a model is presented that extends the multi-regime two-fluid model by a hybrid model for wall-bounded liquid films. Thus, wall films of varying film thickness and length scales can be considered in the Euler–Euler framework. The two-fluid film model (TFFM) is implemented in Star-CCM+ v15.04 and compared against experimental data for horizontal annular flow through an orifice and an expansion. It is found that the presented model can qualitatively reproduce the measured mean liquid volume fraction and film thickness profiles, including film separation and transition to stratified flow. Spurious entrainment of liquid in the gas core, however, deteriorates the quantitative agreement with the experimental data, which can be attributed to limitations in the current model implementation. Finally, the presented model is applied to the simulation of a water separator and compared to a simulation without a hybrid film model. A significant improvement in the predicted phase field and separation efficiency was found with the TFFM, which justifies further research to alleviate the current model limitations.