Prediction of Deepwater Oil Offloading Buoy Response And Experimental Validation

Fully coupled time-domain approaches were applied to predict the vertical plane motions, i.e. surge, heave and pitch, of the deepwater buoy. It is found that the pitch motion in particular is sensitive to the drag effect of the skirt, and is coupled with both surge and heave motions, and that a time-domain fully coupled analysis can capture the viscous drag effect. Results from 2 experiments, one with a freely floating buoy and the other with a moored buoy, are presented to show that the proposed time-domain coupled analysis predicts the buoy motion behavior very well for both cases compared to frequency-domain analyses with a linearized stiffness for the mooring system. Comparison of experimental data and coupled analysis results from the proposed buoy skirt modeling with multiple disks shows that viscous modeling of the buoy skirt by applying a Morison drag force formulation based on relative velocity can be used to better predict the pitch motion.