The motions and drift forces of side-by-side (SbS) moored FSRU (Floating Storage & Regasification Unit) and LNGC (Liquefied Natural Gas Carrier) including sloshing are studied by numerical methods and experiments. FSRU and LNGC have LNG cargo tanks and sloshing affects the motions due to the coupling between sloshing and floating body motions. Gap flow also affects the motions and drift forces of FSRU and LNGC. Sloshing is calculated by the pendulum model and NS (Navier-Stokes) VOF (Volume of Fluid) method. The effect of sloshing on the surge, sway motion and drift forces is confirmed. The numerical results agree with the experiments. It is noted that sloshing occurs in longitudinal mode and affect the surge motion and mooring load.


The side-by-side offloading operation of LNG can be influenced by many factors; LNG sloshing, gap flow between two bodies, mother ship's mooring system, Ship to Ship (STS) mooring system, and environments etc. Sloshing affects the motion; particularly roll and sway motion. Gap flow also influences the sway motion and mean drift force. So sloshing and gap flow must be considered simultaneously with ship motions. There are two ways to consider sloshing; model test and numerical analysis. The disadvantages of experiment are the expensive cost, limited test case and difficulty of similarity of LNG. Numerical method has the advantages of the disadvantages of model test. The coupling analysis of sloshing and motions is studied by many researchers. The representatives are Faltinsen and Timokha (2009), Kim, Nam, Kim and Kim (2007), Kim and Shin (2008), Lee, Godderidge, Tan, Temarel, Turnock and Cowlan (2009), and Gaillarde, Ledoux and Lynch (2004). They show the good results but only are restricted to 1 body. The coupling of sloshing and 2 body is recently reported by Cho, Sung, Hong and Hong (2011).

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