﻿ FLNG尾输过程耦合运动分析
 舰船科学技术  2021, Vol. 43 Issue (7): 64-69    DOI: 10.3404/j.issn.1672-7649.2021.07.013 PDF
FLNG尾输过程耦合运动分析

1. 中海油研究总院有限责任公司，北京 100028;
2. 天然气水合物国家重点实验室，北京 100028;
3. 国家能源深水油气工程技术研发中心，北京 100028

Research on the coupled motion response of a FLNG in tandem offloading process
ZHAO Jing-rui1,2,3, Li Qing-ping1,2,3, WANG Shi-sheng1,2,3
1. CNOOC Research Institute Ltd, Beijing 100028, China;
2. National Research and Development Center for Energy Engineering Technology in Deep Water, Beijing 100028, China;
3. National Energy Deepwater oil and Gas Engineering Technology Research and Development Center, Beijing 100028, China
Abstract: The dynamic characteristics of FLNG are studied during tandem offloading operation by using numerical method. The coupled hydrodynamic results of FLNG and LNG carrier are calculated according to the middle field theory, and the coupled model include FLNG, LNG carrier, single point mooring system and hawser lines is established and the responses are obtained. The result shows that during the tandem offloading process of FLNG, the coupled hydrodynamic effects will occur and the no-coupled hydrodynamic model will overestimate the drift force acting on the two vessels especially for LNG carrier. The wind and current can improve the stability of the whole system and reduce the risk of collision.
Key words: FLNG     coupled hydrodynamic response     tandem offloading operation     middle field theory
0 引　言

FLNG是一种集海上天然气生产、储存、外输功能于一身的新型海工装备。目前FLNG采用的外输方式有旁靠外输和尾输2种，其中尾输方式由于作业时两船相对距离远，作业时容许的环境载荷更大，被认为更适合在环境条件相对恶劣的海区应用。

1 设计基础 1.1 FLNG与LNG运输船

FLNG主尺度参数为船长340.0 m，船宽61.0 m，型深37.0 m，有10个GTT液舱，整体LNG容积为252000 m3。LNG运输船主尺度参数伟船长291.0 m，船宽47.0 m，有4个GTT液舱，LNG容积为173500 m3。FLNG与LNG运输船的总布置图如图1所示。FLNG与LNG运输船在外输过程中具有3种典型装载组合，具体参数如表1所示。

 图 1 FLNG与LNG运输船总布置图 Fig. 1 Main arrangement plan of FLNG and LNG carrier

1.2 FLNG单点系泊系统

FLNG采用15根系泊缆绳呈3组进行定位，所有缆绳在分段结构上完全相同，主要分为3段，包括顶部锚链，中部钢缆与底部锚链。底部锚链长1392 m，直径为146.05 mm，破断拉力为18908 kN，中部由螺旋钢缆组成，长1859 m 直径139.7 mm，破断拉力为19186 kN，顶部锚链与底部锚链规格相同，长100 m。缆绳几部分之间采用卸扣连接，每根缆绳采用吸力锚定位，系泊水平跨距为2815 m，顶部预张力约为5150 kN。

1.3 尾输系泊系统

2 耦合系统数值模型 2.1 水动力分析模型

 图 2 FLNG和LNG运输船的水动力模型 Fig. 2 Hydrodynamic model of FLNG and LNG carrier

 图 3 两船体之间水面的划分 Fig. 3 Mesh model of water plane between FLNG and LNG carrier

FLNG与LNG运输船船体上的2阶波浪漂移力根据中场理论计算，为了考虑两船体水动力的耦合作用，需要对船体之间的水面进行网格划分并给定能量耗散系数（通常根据水池模型试验获得），以抑制此区域内的波面共振。

2.2 耦合水动力分析分析

 图 4 FLNG单点系泊系统布置 Fig. 4 Single point mooring system of FLNG

 图 5 尾输系泊系统 Fig. 5 Tandem mooring system
3 结果与讨论 3.1 水动力敏感性分析

 图 6 两船垂荡运动RAOs对比 Fig. 6 Heave RAO comparison of two vessels

 图 8 两船纵荡漂移力RAOs对比 Fig. 8 Surge drift force RAO comparison of two vessels

 图 7 两船纵摇运动RAOs对比 Fig. 7 Pitch RAO comparison of two vessels

 图 9 两船垂荡运动RAOs对比 Fig. 9 Heave RAO comparison of two vessels

 图 11 两船纵荡漂移力RAOs对比 Fig. 11 Surge drift force RAO comparison of two vessels

 图 10 两船纵摇运动RAOs对比 Fig. 10 Pitch RAO comparison of two vessels

 图 12 两船垂荡运动RAOs对比 Fig. 12 Heave RAO comparison of two vessels

 图 13 两船纵摇运动RAOs对比 Fig. 13 Pitch RAO comparison of two vessels

 图 14 两船纵荡漂移力RAOs对比 Fig. 14 Surge drift force RAO comparison of two vessels

3.2 耦合分析结果

 图 15 两船之间距离时间历程 Fig. 15 Time history of distance between two vessels

 图 16 两船之间距离频谱 Fig. 16 Spectrum of distance between two vessels

 图 18 系泊缆张力距离频谱 Fig. 18 Spectrum of hawser tension

 图 17 系泊缆张力时间历程 Fig. 17 Time history of hawser tension

 图 19 5种典型外输作业环境载荷方向组合 Fig. 19 Five typical directional combination in tandem offloading operation

4 结　语

1）根据中场理论，在FLNG进行尾输过程中FLNG船体与LNG运输船将出现水动力耦合效应，非耦合水动力分析将高估作用于LNG运输船体上的纵荡漂移力。在对水动力分析的影响因素中，波浪入射角度对结果的影响最大，其次为两船之间的相对距离，而装载工况组合的影响最小。

2）在纯波浪工况下，两船之间的相对距离范围较大并可能导致两船碰撞，而风流载荷将在某种程度上降低两船体相对运动和系泊张力的变化范围，改善整体系统的稳定性。

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