Modelling horizontal two-phase flows using generalized models

Gas-liquid two-phase flows in the hot leg of a pressurized water reactor (PWR) under hypothetical accident scenarios have received special attention in nuclear reactor safety research. The numerical simulation of such flows can be performed using phase-averaged multi-fluid models, such as the two-fluid approach, or non-phase-averaged alternatives. The method shown in this paper within the two-fluid framework is the Algebraic Interfacial Area Density (AIAD) model. It features the macroscopic blending between different interfacial area density and momentum transfer models depending on the local flow morphology. The work presented here strives to improve the turbulence modelling for free surface flows by introducing a model for sub-grid size waves induced by Kelvin-Helmholtz instability. A first CFD validation of the methodology is done by means of horizontal, adiabatic, stratified flow data from the WENKA facility. More verification and validation of the approach is required - more CFD grade experimental data is the key to further validation.