TransAT CMFD (Computational Multi-Fluid Dynamics) code was employed to simulate various types of multiphase flows in horizontal and vertical pipes, under distinct flow regimes. Within the Interface Tracking concept (ITM), use is made of the level set method to track the liquid surface, combined with the Very-Large Eddy Simulation (VLES) approach to cope with turbulence. We will first discuss new results of transition from stratified to slug flow, which agree well with the data as to water hold-up and slug frequency. We will then present new results of bubbly and slug flow evolution in a vertical pipe, comparing the mixture algebraic slip model with the level set approach. The latter technique was also employed for the first time in 3D, revealing a qualitative picture of the flow, very much in accord with the visualizations. Advantages and limitations of each prediction techniques are discussed.


Gas-liquid flows appear in various industrial processes and in the petroleum industry in particular, where mixture of gas and liquids (light and heavy components of oil, solid particles, hydrates, condensate and/or water) are produced and transported together (Hewitt, 2005). In both horizontal and vertical pipe flows, the phases can assume various geometric patterns or topologies (e.g. bubbly, slug, annular, mist) depending on the phasic volumetric flow rates, pipe diameter and inclination. In addition, the relative phasic volumetric fraction can change along the pipes either because of heat addition from outside, heat exchange between the phases or flashing due to depressurization. Current predictive tools for multiphase flow and heat transfer are based on the two-fluid, six-equation model in which the conservation equations of mass, momentum and energy are solved for each phase. In the oil and gas industry this model is reduced to 1D, and is commonly referred to as the "Mechanistic Model".

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