The experimental investigation of flow induced pulsations in corrugated flexible pipes in service with supercritical carbon dioxide

Fluid-structure interaction (FSI) simulations of highpressure multiphase CO2 flow in 2-inch piping were performed to predict flow-induced piping vibration and stress. Computational fluid dynamics (CFD) was used to predict the unsteady multiphase flow in the piping and the flow-induced forces on the bends. A structural finite element model of the 2-inch piping system was loaded with the CFD-predicted flowinduced loading to predict piping vibration and stress in time domain. A one-way FSI simulation approach was adopted, where the flow interacts with the structure, but it is assumed that the vibration of the structure does not affect the flow field. The 2-inch piping system is a high-pressure flow loop where piping vibration and stress were measured for a range of CO2 multiphase flow conditions in a test campaign aiming to characterize piping vibration responses with CO2 as the working fluid. The numerically predicted piping vibration and stress are compared against physical measurements collected during the test campaign at locations where accelerometers and strain gauges were installed. The selected flow conditions are for CO2 in gas and liquid phases with operation at a phase transition condition of 55 bara and 18°C. Simulations are performed for three flow conditions with increasing gas rate and fixed liquid rate, resulting in flows with decreasing liquid content by volume: 12.5%, 8.85%, and 6.73%. We find good agreement when comparing the predicted vibration levels against those measured by the accelerometers and find that the predicted stress is conservative relative to the stress measured by the strain gauges. The results validate the FSI predictions and instill confidence in the simulation approach, which is recognized as a powerful tool to predict flow-induced vibration of piping in multiphase systems.