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

Abstract

These recent years, several experimental investigations were carried out on horizontal gas-liquid two-phase sub-regimes including plug, Less Aerated Slug (LAS) and Highly Aerated Slug (HAS) flows. Such classification is based on the shape of the elongated bubble/liquid slug interface as well as the aeration in the liquid slugs. In this paper, an extensive experimental visualization was performed using air-water mixture in a 30 mm ID horizontal pipe covering a total of 189 operating conditions. It was reported, for the first time, that each sub-regime had a specific mechanism of aeration of the liquid slug flow. For instance, the presence of gas bubbles within liquid slugs, in 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 shearing-off and scooping mechanisms of bubbles, in the liquid film, into the liquid slug, respectively. In addition, the reported flow transition lines, as well as those existing in the literature, were analyzed using different existing coordinate systems. This analysis showed that the X-T system is the most suitable for predicting the three flow sub-regimes.