Experimental investigation of induced vibrations in horizontal Gas-Liquid flow

Abstract

One of the governing contributors to offshore structures' (e.g., pipelines and deep-water risers) accumulative long-term fatigue damage is the internal flow-induced vibrations caused by slug flow. Due to the complexity of the numerical modeling of the internal flow and fluid–structure interaction, experimental campaigns are often performed to predict the asset response and provide a benchmark for numerical model validation. In this study, an experimental campaign was conducted which included a unique computer vision data acquisition system and a large-scale facility designed to mimic industry field conditions. This study aims to relate flow parameters to structural response and explain the mechanisms that govern the relationship between both domains.The presented results reveal that the gravitational forces of the fluid dominate the transverse deflections of the pipe and, therefore, the slug liquid holdup, film liquid holdup, and slug length showed strong correlations to pipe deflections. However, centrifugal forces were observed to have significant contributions to pipe deflection for high translational velocity slugs. Additionally, it was found that for most of the test conditions, the primary pipe excitation frequency correlates to the slug frequency. It was discovered that no-slip liquid holdup has a positive correlation to both the magnitude and range of pipe deflection and that increases in superficial gas and liquid velocities led to decreases and increases in pipe deflection, respectively. Furthermore, it was observed that the measured frequency responses of the structure tended to increase with increasing gas velocity until the flow pattern in the pipe began to transition to annular flow.