On Roll Hydrodynamics of FPSO’s Fitted With Bilge Keels and Riser Balcony

The topic of this paper is the roll motion prediction of ship-shaped FPSO’s, designed for continuous operation at site location. The maximum roll amplitude is a critical operability parameter which is difficult to predict accurately due to the nonlinear roll damping associated with the appendages. This paper contributes to the understanding of roll damping physics through model test results, CFD simulations and potential flow predictions. The model tests discussed concern two different Floating Production, Storage and Offloading (FPSO) units, designed by SBM as spread-moored units for operation offshore Brazil. The relevant roll damping appendages are the bilge keels on both sides and the submerged riser balcony on one side of the vessel. In particular the riser balcony complicates the motion prediction and was a main reason for the model tests and CFD investigation. The results presented focus on roll motion prediction in the frequency domain.