Dynamic Asynchronous Coupled Analysis and Experimental Study for a Turret Moored FPSO in Random Seas

The dynamic coupling analysis between floating platform and mooring/risers is one of the challenging topics in development of oil and gas exploration in deepwater area. In this paper, the dynamic coupled analysis model for a turret-moored floating production storage and offloading (FPSO) is developed. In order to improve the computational efficiency, the proposed asynchronous coupling model is extended to application for FPSO coupled dynamic analysis. In order to validate the developed dynamic coupling analysis model, the vessel global motion and mooring tensions for the turret moored tanker KVLCC2 were tested in China Ship Scientific Research Center (CSSRC) wave basin. In this paper, the numerically predicted coupled response is directly compared with those from model test in time domain. The research focus is in the following: (1) Through comparison of free decay surge motion in calm water/regular wave, the damping effect from mooring on drift motion is validated and confirmed; (2) The physical phenomena of wave drift damping effect on slowly varying surge motion are theoretically explained making use of the related hydrodynamic model and physical model test; (3) In random seas, the simulated vessel motions and mooring tensions generally show fairly good match in time records with model test. But there is phase difference between simulation and measurements after tens of minutes in model test scale, the exact reason is not known yet; and (4) Another interesting phenomena in model test are the existence of unstable horizontal sway and yaw motion, which are not well predicted by current numerical model, the further research is needed.