Liquid-Gas Flow-Induced Vibration in Flexible Pipe*

Liquid-gas flows propagating through a pipe may evolve into a variety of flow patterns governed by the flow-pipe parameters and interfacial characteristics. Mechanisms of liquid-gas flow-induced vibrations in a long flexible pipe with a high length-to-diameter ratio are poorly understood owing to the lack of studies dealing with such complex flow phenomena inside the bendable geometries. Previous studies have mostly focused on a rigid inflexible pipe with a short span, small diameter or fixed inclination. Here, the most problematic slug flows with fluctuating liquid-gas volumetric fractions, velocities and pressure are studied through a hierarchy of mathematical, phenomenological and computational fluid dynamics models. We predict liquid-gas flow features and effects on flexible pipes with variable inclinations, multiple bends and multi-directional flows, and assess the pipe dynamic deformations, stresses and frequencies. The effects of slug properties (length, velocity, frequency, intermittency) are investigated. Numerical results reveal several key fundamental aspects of flexible pipe vibrations caused by travelling liquid-gas slug flows.