The Effects of Tank Sloshing on the Coupled Responses of LNG Vessel and Floating Terminal
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The hydrodynamic interactions between FT (Floating Terminal) and LNGC(Liquefied Natural Gas Carrier) in side-by-side offloading arrangement as well as the dynamic coupling between the floating-body motion and inner-tank sloshing are investigated by a potential-viscous hybrid method in time domain. For the time domain simulation of the vessel motion, the hydrodynamic coefficients and wave forces are obtained by a potential-theory-based 3-D diffraction/radiation panel program in frequency domain. The ensuing simulations of vessel motions in time domain are carried out by using an impulse response function approach. The liquid sloshing in inner tanks is simulated in time domain by a FDM Navier-Stokes solver with SURF scheme. The computed sloshing forces and moments are fed into the time integration of ship motion, and the updated ship motion is in turn used as the excitation force for liquid sloshing, which is repeated for the ensuing time steps. For comparison, we independently developed a sloshingmotion coupled analysis program based on linear potential theory in the frequency domain. The developed computer programs are applied to the side-by-side offloading operation between the FT and LNGC. The frequency-domain results qualitatively reproduce the coupling effects but the peaks are in general over-predicted compared to experimental and time-domain results. The liquid-sloshing and vessel-motion interaction effects can further be intensified in the case of multiple floating bodies. Copyright 2008 by The International Society of Offshore and Polar Engineers (ISOPE).