Numerical simulation of an horizontal counter-current two-phase flow experiment using an interfacial area density model

In order to improve the understanding of counter-current two-phase flows, a CFD simulation of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular cross section was performed. A selected air-water counter-current flow limitation (CCFL) experiment at the Forschungszentrum Dresden-Rossendorf (FZD) at 0.306 MPa and room temperature (experimental running of 30-05) was calculated with three-dimensional two-fluid models of computer code ANSYS CFX 13. It was simulated using the multi-fluid Euler-Euler modeling approach. The transient calculation was carried out using a gas/liquid inhomogeneous multiphase flow model coupled with a SST turbulence model for each phase. In the simulation, the surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD) model. The AIAD model allows the detection of the morphological form of the two phase flow and the corresponding switching via a blending function of each correlation from one object pair to another. As a result this model can distinguish between bubbles, droplets and the free surface using the local liquid phase volume fraction value. A comparison with the high-speed video observations shows also a good qualitative agreement (Fig. 1). The results indicated also that quantitative agreement of the CCFL characteristics between calculation and experimental data was obtained.