Transient Hydrodynamic Forces on a Disconnectable Turret Buoy

For disconnectable turret-moored FPSOs, accurate prediction of turret buoy and FPSO motions during the buoy disconnection process is essential for safe operations. For deepwater high production rate systems, large size buoys are required to accommodate the large number of risers and heavy mooring legs. Analytical models of hydrodynamic forces on large size buoys must be verified before they are applied to motion predictions. To gain a better understanding of the transient hydrodynamic loads on the buoy and hydrodynamic interactions between the buoy and the hull during disconnection, we conducted a specially designed model test in a tow tank. In the model tests, both the buoy and the FPSO models were forced to oscillate by two independent actuators in calm water and in waves. Summary of test results, computed transient hydrodynamic forces from a simplified approach, a true time-domain transient hydrodynamic analysis based on instantaneous buoy positions, and computational fluid dynamics (CFD) results are presented in this paper.