Slug Frequency in Horizontal Pipeline Subject to a Sudden Contraction: State of the Art and Laboratory Testing Data

Liquid-gas two-phase flows are widely encountered in industrial applications including chemical processes, petroleum engineering and energy manufacturing units systems. Of all flow patterns encountered in field operations, slug flow is the dominant one in horizontal and near horizontal pipelines, and is also the most complicated one. Of all flow topological configurations, slug flow is the most concerning from the operational perspectives. It is characterized by an alternate flow of liquid slugs and gas pockets, resulting in an inherently unsteady hydrodynamic behavior. Frequency of the slug has important significance on gas-liquid two-phase flow. This paper presents the results of experimental study of gas-liquid slug flow in a horizontal pipe subjected or not to a sudden contraction. The first objective of this study is to present a state -of -the art of correlations concerning slug frequency; an analysis on the accuracy of these correlations is performed based on direct comparison against experimental data. It has been found that none of the slug frequency correlation was able to produce accurate prediction. In this study, the effects of sudden contraction on slug frequency regime were also investigated experimentally through the analysis of slug persistence and frequency, it has been found that: i) the slug flow prevails before and after the contraction, ii) frequencies of the structures persist across the contraction.