Gas-liquid two-phase flow occurs in a wide range of engineering applications in various industrial fields. For example, without being exhaustive, in the chemical and process industry, a two-phase flow is encountered in boilers, condensers, evaporators and reactors. In the petroleum industry, a two-phase flow is observed during the production and transportation of oil and gas.Among flow patterns encountered in field operations, the slug flow appears to be dominant in horizontal and near horizontal pipelines, and is, unfortunately, the most complicated one. It is characterized by an alternate flow of liquid slugs and gas pockets, resulting in inherently unsteady hydrodynamic behavior. All the important design variables, such as gas and liquid velocity profiles, liquid holdup distribution and pressure drop vary axially and radially and exhibit fluctuations, even when the inlet liquid and gas flow rates are constant. This makes prediction of slug flow characteristics complex and challenging. This paper is therefore devoted to slug flow in horizontal pipelines and attempts to address the above-cited points. Specifically, the study aims to develop a map of flow regimes then acquire pertinent slug flow data. For that purpose, an experimental test rig was built-up to examine the process of slug initiation in a 40 mm i.d and a 14 m length horizontal pipeline. Two-phase cocurrent air-water pressure gradients were measured. Most of the data recorded correspond to the slug flow region, noting then rapid fluctuations in pressure. Data on slug initiation, pressure variation as well as slug frequency and length are investigated and reported hereafter.

In many industrial processes, the presence of liquid and gas mixtures creates a slug flow. This kind of regime is observed when slug's liquid blocks the whole pipeline and moves as a coherent mass downstream at a velocity approximately equal to the gas velocity. The aim of this study is to provide statistical information on slug in two-phase flow in horizontal pipe. Experiments were conducted in a pipe of 0.04 m diameter and a length of 14 m. First of all, a flow regime map is compiled for air/water two phase flows. Data on pressure gradient, slug frequency and liquid holdup are presented. It was found that mean slug frequency clearly increases as the superficial liquid velocity increases but it weakly depends on the superficial gas velocity.

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Two-phase flows are encountered in a wide range of industrial application. In the present work, two-phase computational fluid dynamics (CFD) calculations, using Eulerian-Eulerian model and commercial CFD package FLUENT 6.3, were employed to calculate pressure drops caused by abrupt flow area contraction in small circular pipes for two-phase flow of air and water mixtures at room temperature and near atmospheric pressure. The pressure drop is determined by extrapolating the computed pressure profiles upstream and downstream of the contraction. Variables studied include: gas and liquid velocities, and pipe contraction ratio. The numerical results were validated against experimental data from the literature and are found to be in good agreement. Our findings could be useful in designing pipeline.