KEYWORDS: FPSO, Moonpool Oscillations, CFD, Sloshing, Ship Resistance

The hydrodynamic behaviour of moonpool oscillations in large FPSO (Floating Production Storage and Offloading) vessels is investigated through computational analysis and scale-model laboratory experiments. The computational analysis is carried out using the STAR-CCM+ software. The scale-model experiments were carried out in (90.0 m x 4.0 m x 3.0 m) wave flume with a flap wavemaker and in (88.0 m x 3.2 m x 2.6
m) towing tank in the Ocean Engineering Department of IIT Madras. Of particular focus of the study has been on the generation of moonpool oscillations by ambient waves and ship motion and the influence of moonpool oscillations on the FPSO ship resistance. Geometrically the moonpool is modelled as the annular gap between concentric cylinders and is located at the front of a large FPSO platform. The computational and experimental analyses are carried for a range of parameters, such as amplitude and frequency of wave motion, forward speed, and geometry of moonpool entry. The numerical and experiments results compare reasonably well, though not quantitatively exactly, as elaborated in the paper. Several interesting flow physics, for example, the excitation of moonpool oscillations by the vortices shed at the edge of moonpool entry, are revealed in the study. Flow visualization from CFD reveal complex vortex and flow interactions resulting from the moonpool oscillations. Experiments were conducted both with and without moonpool, and the results confirm that moon pool oscillation augments the resistance of the FPSO. Ongoing and future studies on the topic are also discussed