In the oil field industry multi-phase flows are commonly present at production and transportation facilities. For gas/liquid mixtures, different flow structures can occur, dependent on the phase velocities, the operating, the geometrical dimensions and inclination angles of the pipelines. The interdepen-dency of these parameters is reflected in so-called flow pattern diagrams. These flow patterns are generally used to predict two-phase flow behavior. Various flow regimes can be distinguished in two-phase flow: dispersed, separated, and intermittent flow. Intermittent flow is the most problematic flow regime since this may pose serious problems to the designer and operator of two-phase flow lines. Large and fluctuating rates of gas and liquid can occur and dramatically decrease the production and in the worst case can cause damage and/or shut down of separation facilities. In the present article, the fluid dynamics of gas liquid slug flows in horizontal and inclined pipes are investigated using 3D Computational Fluid Dynamics (CFD) software. The two-phase Volume of Fluid model (VOF) has been used to predict the transition of segregated gas liquid flow into slugflowpat-terns and a number of cases has been studied using different pipeline geometries. A set of simulation runs was performed to compute flow patterns in horizontal and inclined gas-liquid pipelines. The first set of runs was done using a horizontal pipe with a 2-inch diameter and the results were verified against experimental work done recently. It covers a wide range of flow rates and the superficial velocities of the gas and liquid phases. Stratified flow conditions as well as slug flow characteristics have been calculated and new relations between the superficial liquid velocity, pressure drop and liquid hold up have been derived. The ultimate aim of this work was to gain a deeper understanding of multiphase flow phenomena in pipelines and to develop guidelines to improve the design of pipelines and separation facilities.
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