Fluid-structure interaction analysis on vibration characteristics of flexible risers conveying gas–liquid two-phase flow

To investigate the fluid-structure interaction effect of gas–liquid two-phase flow-induced vibration of flexible risers, experimental research is conducted using the non-intrusive measurement techniques. The high-speed camera and pressure sensors are used to capture the vibration displacements, internal flow structures, and pressure variations. The experimental results indicate that the distribution of the excitation forces is influenced by the catenary shape, thereby affecting the spanwise evolution of vibration displacements. The vibration response is found to be related to the flow process of liquid slugs, with the vibration response attaining its maximum amplitude when a liquid slug flows through. Conversely, the departure of a liquid slug results in a decrease in the vibration response. The occurrence of frequency components close to the natural frequency and the dominant frequency of flow characteristics indicates that the vibration response, pressure variations, and evolution of flow structures interact with each other in the process of flow-induced vibration. Under the combined action of pressure variations and mass distributions, the vibration response initially rises and then decreases as the superficial velocity of liquid increases. The correlation analysis indicates that the degree of influence exerted by mass distributions on the vibration response is stronger than that of the pressure variations.