Experimental investigation on interface characteristics of gas-liquid two-phase flow in a kilometer-scale pipeline

It is greatly essential for the construction of multiphase flow models and the flow assurance of oil and gas pipelines to study the fully developed interface characteristics at different flow patterns in the industrial-grade long-distance pipelines. In this paper, the phase interface structures of dispersed bubble flow and three slug subflow patterns are captured by visualization method in a 46 mm ID, 1657 m long pipeline. It is found that the interface characteristics between elongated bubbles and liquid film can effectively distinguish different slug subflow patterns, and a quantitative division criterion between different slug sub-flow patterns is proposed. The transition boundary prediction model for dispersed bubble flow and slug flow in long pipeline is established, and the flow pattern map at high liquid velocities and low gas velocities is plotted. With the increase of two-phase mixture velocity, the radial position of elongated bubble head approaches the middle of the pipeline, and the liquid film thickness is stably distributed around 0.37 D. The correlations that predict the radial position of elongated bubble head, liquid film thickness, and elongated bubble velocity for long pipeline are established, with maximum error less than 15 %.