The motions and mooring loads of turret moored FSRU (Floating Storage & Regasification Unit) and LNGC (Liquefied Natural Gas Carrier) including sloshing are studied by experiments. Turret moored FSRU weathervanes on a turret and side-by-side (SbS) LNGC moves and interacts with FSRU. FSRU and LNGC have LNG cargo tanks and sloshing affects the motions and loads due to the coupling between sloshing and floating body motions. The performance of FSRU and LNGC offloading system is investigated through the assessment of global motions, accelerations, mooring loads and Ship-To-Ship (STS) loads. It is noted that although the direction of head moves to bow quartering, the sloshing occurs in longitudinal mode and affect the surge motion and mooring load. STS mooring affects the sway and roll motion of LNGC and interacts with LNGC sloshing.
The side-by-side offloading operation of LNG can be influenced by many factors; mother ship's mooring system, STS mooring system, gap flow between two bodies, LNG sloshing, and environments etc. The performance of offloading operation is decided by the operation possibility (downtime) of LNG offloading system. The criteria of offloading operation are the relative motions of surge, sway and heave and the forces of fender and mooring rope. To assess the offloading operation precisely, the factors which influence motions and mooring loads should be considered. Representative studies for the side-by-side transportation are Voogt (2010, 2009), Jeong (2010), Hansen (2009), Hong (2009), and Wilde (2009). The previous works report the results without sloshing. But Cho (2011) presented that the longitudinal sloshing affect the motions of SbS FSRU and LNGC. Also the drift forces are changed by the coupled motions with sloshing. In order to investigate the important factors of offloading operation, experiments were carried out at KORDI (Korea Ocean Research & Development Institute)'s ocean engineering basin.