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Lookup NU author(s): Professor Zhiqiang Hu
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).
Integrated dynamic responses of FLNG system in side-by-side offloading operation are investigated numericallyand experimentally in this paper. A numerical code is developed based on potential flow theory to predict theinteractions between connected vessels' motions and liquid sloshing in the time domain. The impulsive responsefunction (IRF) method is adopted in the resolution for 6 DOF vessels' motions, nonlinear sloshing in liquid tanksis solved using boundary element method (BEM), and connection system including hawsers and fenders is numericallymodeled as linear response system. A series of model tests are conducted to validate the feasibility ofthe numerical code. Hydrodynamic interaction between the vessels and shielding effects under different wavedirections are analyzed; sloshing effects on the vessels' motions and on the loads of connection system areinvestigated; the sensitivities of the vessels' motions and loads to connection system stiffness are discussed. It isfound that the vessels' motions are significantly affected by the hydrodynamic interactions between vessels andsensitive to wave directions for shielding effects. The radiation forces of the adjacent vessel tend to amplifyvessel's motions and LNG carrier is more likely to be affected by FLNG's radiation forces for their difference indisplacement. In addition, compared with solid loading condition, liquid loading vessel tends to have decreasednatural roll frequency and have increased sway motions in the frequency region that higher than the naturalsloshing frequency. The two sloshing responses peaks appear in the natural roll frequencies and natural sloshingfrequencies, which are respectively mainly excited by vessels' roll and sway motions. Besides, in low fill conditions,the sloshing loads contribute to larger sway motions in low fill conditions for the natural sloshingfrequencies are closer to the main response frequency region of vessels. Sloshing nonlinearity gets obvious in theconditions with low fill conditions and large wave amplitude, while the motion responses of vessels have slightnonlinearity with the increases of sloshing nonlinearity when no violent sloshing with wave break is excited.Furthermore, small stiffness of the connection system has slight influences on the vessels' motions, and resonantmotions can be excited when the natural frequency of the connection system located in the wave frequencyregion.
Author(s): Zhao D, Hu Z, Zhou K, Chen G, Chen X, Feng X
Publication type: Article
Publication status: Published
Journal: Ocean Engineering
Print publication date: 15/11/2018
Online publication date: 11/09/2018
Acceptance date: 09/08/2018
Date deposited: 01/10/2018
ISSN (print): 0029-8018
ISSN (electronic): 1873-5258
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