Analysis of Horizontal Gas-liquid Intermittent Flow Sub-Regimes Transitions: Physical Mechanisms and Flow Maps

Abstract

Abstract These recent years, several experimental investigations were carried out on horizontal gas-liquid two-phase flow by considering the sub-regimes which are plug, Less Aerated Slug (LAS) and Highly Aerated Slug (HAS) flows. These sub-regimes classification is based on the shape of the elongated bubble/liquid slug interface as well as the aeration within liquid slugs. In this work, an extensive experimental visualization was performed using air-water mixture in a 30 mm ID horizontal pipe. The study has covered a total of 189 operating conditions. It was reported, for the first time, that each sub-regime had a specific mechanism for aeration of the liquid slug flow. the presence of gas bubbles within liquid slugs, in the case of plug flow, is due to the interfacial shear induced waves mechanism. The transitions to LAS and HAS flows are accompanied by the appearance of the shearing-off and scooping of the bubbles present in the liquid film into liquid slug mechanisms, respectively. In addition, the reported flow transition lines, as well those existing in the literature, were analyzed using different existing coordinate systems. This analysis allowed finding that the X-T system is the most suitable one for predicting the three flow sub-regimes.