Effects of vessel-pipe coupled dynamics on the discharged CO2 behavior for CO2 sequestration

This study examines the behaviors and properties of discharged liquid CO2 from a long elastic pipe moving with a vessel for the oceanic CO2 sequestration by considering pipe dynamics and vessel motions. The coupled vessel-pipe dynamic analysis for a typical configuration is done in the frequency and time domain using the ORCAFLEX program. The system\' s characteristics, such as vessel RAOs and pipe-axial-velocity transfer function, are identified by applying a broadband white noise wave spectrum to the vessel-pipe dynamic system. The frequency shift of the vessel\' s RAO due to the encounter-frequency effect is also investigated through the system identification method. Additionally, the time histories of the tip-of-pipe velocities, along with the corresponding discharged droplet size and Weber numbers, are generated for two different sea states. The comparison between the stiff non-oscillating pipe with the flexible oscillating pipe shows the effect of the vessel and pipe dynamics to the discharged CO2 droplet size and Weber number. The pipe\'s axial-mode resonance is the leading cause of the fluctuation of the discharged CO2 properties. The significant variation of the discharged CO2 properties observed in this study shows the importance of considering the vessel-pipe motions when designing oceanic CO2 sequestration strategy, including suitable sequestration locations, discharge rate, towing speed, and sea states.