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J. Ocean Eng. Technol. 2010;24(5):16-21.    

The Effects of Sloshing on the Responses of an LNG Carrier Moored in a Side-by-side Configuration with an Offshore Plant
Lee Seung-Jae
American Bureau of Shipping
해양플랜트에 병렬 계류된 LNG 운반선의 거동에 슬로싱이 미치는 영향
이승재
미국선급협회
Copyright © 2010 The Korean Society of Ocean Engineers     Open access / Under a Creative Commons License
Key Words: Sloshing, Global motion, Coupled dynamic analysis, Time domain potential-viscous hybrid method
핵심용어: 슬로싱, 거시적 운동, 동적 연성 해석, 시간영역 포텐셜-점성 혼합 방법
Abstract
During the loading/offloading operation of a liquefied natural gas carrier (LNGC) that is moored in a side-by-side configuration with an offshore plant, sloshing that occurs due to the partially filled LNG tank and the interactive effect between the two floating bodies are important factors that affect safety and operability. Therefore, a time-domain software program, called CHARM3D, was developed to consider the interactions between sloshing and the motion of a floating body, as well as the interactions between multiple bodies using the potential-viscous hybrid method. For the simulation of a floating body in the time domain, hydrodynamic coefficients and wave forces were calculated in the frequency domain using the 3D radiation/diffraction panel program based on potential theory. The calculated values were used for the simulation of a floating body in the time domain by convolution integrals. The liquid sloshing in the inner tanks is solved by the 3D-FDM Navier-Stokes solver that includes the consideration of free-surface non-linearity through the SURF scheme. The computed sloshing forces and moments were fed into the time integration of the ship's motion, and the updated motion was, in turn, used as the excitation force for liquid sloshing, which is repeated for the ensuing time steps. For comparison, a sloshing motion coupled analysis program based on linear potential theory in the frequency domain was developed. The computer programs that were developed were applied to the side-by-side offloading operation between the offshore plant and the LNGC. The frequency-domain results reproduced the coupling effects qualitatively, but, in general, the peaks were over-predicted compared to experimental and time-domain results. The interactive effects between the sloshing liquid and the motion of the vessel can be intensified further in the case of multiple floating bodies.


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