Simulations Of Two Phase Flows Using Interfacial Area Transport Equation

Abstract: The current study focuses on providing a reliable computational fluid dynamics (CFD) tool for two-phase flow simulations, which is capable of capturing dynamic changes of interfacial structures and achieving accurate predictions of flow behaviors. A set of interfacial area transport equations (IATEs), which dynamically evaluates the interfacial area concentration, was successfully implemented into a CFD software package, namely, Fluent. The interfacial area concentration is a key parameter in modeling the interfacial transfer terms in the two-fluid model due to mechanical and thermal non-equilibrium between the two phases. Given the various flow regimes in two-phase flows, one-group IATE and two-group IATE developed in the literature were separately incorporated into the two-fluid model and subsequently validated under different flow conditions: liquid-liquid two-component bubbly; air-water bubbly, cap-bubbly, and churn-turbulent flows. Numerical results obtained from the two-fluid model incorporated with the IATE models were generally in good agreement with the experimental data. A set of adjustable model coefficients was also established for three-dimensional simulations when the influence of the lateral phase distribution in a circular flow channel on the one-group IATE model was considered. In addition, contributions of the bubble interaction mechanisms and interfacial forces to the phase distributions of two-phase flow were numerically investigated. It was observed that the lift force was significant for the phase distributions in gas-liquid two-phase flows; however it might cause convergence issues when large bubbles exist in the flow field of interest. Furthermore, a mathematical property, i.e., the well-posedness of the proposed one-dimensional three-field model with the two-group IATE model, was studied. The necessary condition to ensure well-posedness was obtained using characteristic analysis. The momentum flux parameters were introduced to help stabilize the proposed model.