Snap Tension in Mooring Lines of Deepwater Platform

Based on the theory of impact dynamics, the motion equations for a mooring line-floating body system before and after impact loading are established with consideration of the viscoelastic property of mooring lines. The factors that influence the taut-slack conditions of a mooring system are analyzed through classifying the taut-slack regions, which are defined by non-dimensional ratios of displacement, frequency, and damping of the system. The mooring system of Jip spar platform is analyzed, and the snap tension characteristics of mooring lines are given. The factors that influence the maximum tension in mooring lines, including the mass of the floating body, length of mooring lines, frequency and amplitude of external excitation, and pretension in mooting lines, are also analyzed through computing the dynamic response of system and parametric study. It is shown that the maximum tension increases with the increasing mass of the floating body, external excitation and pretension. Also, it is found that the influence of the non-dimensional ratio of damping increases with the increase of the pretension in mooring lines.

Probability Distribution of the Hull Motion and Mooring Line Tension of Two Floating Systems

The statistical and distribution characteristics of the responses of a floater and its mooring lines are essential in designing floating/mooring systems.In general,the dynamic responses of offshore structures obey a Gaussian distribution,assuming that the structural system,and sea loads are linear or weakly nonlinear.However,mooring systems and wave loads are considerably nonlinear,and the dynamic responses of hull/mooring systems are non-Gaussian.In this study,the dynamic responses of two types of floaters,semi-submersible and spar platforms,and their mooring lines are computed using coupled dynamic analysis in the time domain.Herein,the statistical characteristics and distributions of the hull motion and mooring line tension are discussed and compared.The statistical distributions of the dynamic responses have strong non-Gaussianity and are unreasonably fitted by a Gaussian distribution for the two floating and mooring systems.Then,the effects of water depth,wave parameters,and low-frequency and wave-frequency components on the non-Gaussianity of the hull motion,and mooring line tension are investigated and discussed.A comparison of the statistical distributions of the responses with various probability density functions,including the Gamma,Gaussian,General Extreme Value,Weibull,and Gaussian Mixture Model(GMM)distributions,shows that the GMM distribution is better than the others for characterizing the statistical distributions of the hull motion,and mooring line tension responses.Furthermore,the GMM distribution has the best accuracy of response prediction.

Dynamic Analysis of Semi-Submersible Production Platform Under the Failure of Mooring Lines

This paper quantitatively studies the transient dynamic response of a semi-submersible production platform with the loss of one or several positioning mooring lines.A semi-submersible platform,production risers,and positioning mooring lines are all included in the numerical simulation.Increased motion of the semi-submersible platform,tension variation of the remaining mooring lines/risers and the risk of mooring line or riser clashing are all investigated through fully coupled time-domain analysis.Combined environmental loads are selected from irregular waves and the steady current varying from very rough to extreme sea conditions.Three dimension radiation/diffraction theories and Morison’s equation are applied to calculate first-order wave force and second-order mean drift force of floating semi-submersible platform.Nonlinear time-domain finite element methods are employed to analyze the behavior of mooring lines and risers.Results show that the failure of mooring lines seriously reduce the platform’s stability performance.The tension of the rest lines is also increased accordingly.Remaining lines which are closer to the failed lines will have larger tension increase to compensate.Line-Line distance provides practical information for the risk of clashing investigation.

Fatigue Analysis of the Taut-Wire Mooring System Applied for Deep Waters

Precisely predicting the fatigue life of taut-wire mooring systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of mooring lines in a rough sea environment especially in deep waters. In this paper, a comprehensive fatigue analysis is performed for a polyester taut-wire mooring system of an FPSO based on the time domain dynamic theory, rainflow cycle counting method and linear damage accumulation rule of Palmgren-Miner. Three influential factors in the fatigue analysis including the pre-tension, dynamic stiffness and T-N curve are investigated in detail. Two polyester T-N curves, one is from the DNV- 0S-E301 and the other is from the API-RP-2SM, are adopted in the calculation. The fatigue analysis of the mooting system after one-line failure is also carried out. The calculation results indicate that the fatigue life is significantly affected by the T-N curve. The fatigue life decreases with increasing pre-tension, and is largely reduced if taking into account the dynamic stiffness caused by cyclic loading. The analysis also proves that one-line failure has remarkable effects on the fatigue lives of other mooting lines. The present parametric and comparative study is believed to be meaningful to further understanding of the taut-wire mooting system for deepwater applications.

基于改进Resnet-LSTM模型的系泊缆仿真张力预测

对海洋浮式平台系泊系统在复杂多变的作业环境受到的线性、非线性作用力进行了预测,预测过程中对长短周期记忆(LSTM)单模型预测网络隐藏层数、迭代次数和学习速率做了优化。提出了具有可变卷积和小波基激活函数的多层特征提取特性和变阈值残差收缩预测功能的混合预测模型,对平台运动响应多点系泊系统整体受力进行非线性映射,分析了多点系泊缆模型,得到了风浪流联合作用下的系泊缆张力值。使用LSTM单模型、Resnet-LSTM混合模型和改进混合模型对系泊力仿真数据集进行训练预测。结果显示:采用Resnet-LSTM混合模型预测准确度可达0.9974,使用可变卷积改进的Resnet-LSTM预测效果优于未改进模型,各项网络参数和预测指标得以优化。证明基于Resnet-LSTM的改进混合预测模型应用在多点系泊系统张力非线性时序特征预测应用方面具有提升网络性能的作用。

Effect of Process Parameters on S-Parameter of Fabric-Based Embroidered Transmission Line

This paper presented a method of fabricating radio frequency( RF) transmission lines by embroidering conductive thread on fabric. A digital embroidery machine was selected to fabricate transmission lines. Effects of the typical process parameters on the S-parameter of these RF transmission lines were tested and discussed. And the results showed that embroidery process parameters such as stitch direction,stitch spacing,stitch length and embroidered tension had significant effects on the RF performance of embroidered transmission lines,of which stitch type was the most important factor for the measured S-parameter of transmission lines.

基于AquaSim软件的浮式钢制网箱新型锚泊系统研究

锚泊系统对于钢制浮式网箱的安全性及成本影响较大,开展锚泊系统研究对于浮式钢制网箱的设计具有重要意义。基于商业软件AquaSim建立浮式钢制网箱数值模型,介绍AquaSim软件计算机理与规范中锚链校核规则;介绍一种新型的锚缆方案,并与传统纯锚链形式的系泊方案进行对比,探究其优劣性;利用控制变量法,研究导缆孔位置对于网箱浮态的影响,研究锚缆数量及锚缆布置角度对于锚链张力的影响,探讨其安全性。由数值模型计算结果可知,在一定的海况条件下,新型锚缆方案比传统的纯锚链方案成本更低,稳定性更好;导缆孔的位置处于网箱底部时,网箱在波流作用下最不易发生触底现象,浮态较为稳定;锚缆数量的减少会急剧增大网箱锚缆在破断工况下的轴向力,导致安全系数急剧下降;锚缆沿着浪流作用力大的方向布置,能够有效增大锚泊系统的安全性。

LNG-FPSO单点系泊系统设计分析研究

LNG-FPSO具有开采、处理液化天然气的功能,并可储存和装卸LNG,由单点系泊系统长期系泊于作业海域。基于BV系泊分析软件ARIANE7.0.2,采用时域计算方法分析了预张力和系泊缆长度等参数对系泊缆最小安全系数和最大躺底长度的影响,结果可为系泊系统的优化提供了一定的参考。

LNG-FPSO外输系统设计分析研究

LNG通过外输系统从LNG-FPSO(简称FLNG)卸载至穿梭LNG船上,外输系统是FLNG的最关键技术之一。分别介绍了旁靠外输和串靠外输的主要特点及目前外输技术的发展现状。简要阐述了旁靠外输系统设计的关键要素,包括系泊布置、碰垫布置等。最后结合实例介绍了旁靠外输系泊计算分析的基本流程,并进行了计算分析,初步结论为旁靠外输系统的设计提供了一定的参考。

不同系泊模式LNG旁靠超大型FSRU系泊系统设计及水动力性能分析

本文采用规范设计、理论分析和数值仿真相结合的方法,建立LNG船与LNG-FSRU两船旁靠系泊的理论和数值分析模型,对LNG旁靠FSRU码头系泊和软钢臂单点系泊两种典型系泊模式下的转运及卸载作业进行数值分析.同时考虑外部海洋环境风、浪、流组合作用下的综合作业工况,确定FSRU与LNG近距离旁靠作业时系泊设备、缆绳种类、固定式和漂浮式护舷的选型和布置,对LNG、FSRU船的运动特性以及运动过程中缆绳张力和护舷受力开展统计分析,优化系泊系统布置和参数.在系泊系统设计和分析的基础上,根据系泊缆的直径、所受最大张力值,为系泊设备选型提供参考,便于开展码头系泊系统和单点系泊系统布置研究.基于旁靠系泊的设计标准提出LNG-FSRU安全作业的最大允许海况,为LNG-FSRU的运营提供可靠的技术保障.

非对称系泊系统布置下Spar平台运动响应分析（英文）

对大陆坡上的油气资源开采时,浮式平台所处位置处的海底地形可能出现较大坡度,需布置非对称的系泊系统。文章基于一个Spar平台,针对平台两侧系泊系统锚固点所处地形变化而造成水深不同的情况,优化设计一套非对称的系泊系统,且非对称系泊系统的水平刚度较大。在时域范围内建立耦合数值模型对平台的运动响应和系泊系统动力特性进行研究和分析。文中研究表明,采用非对称系泊系统的平台在纵荡、横荡和纵摇方向上的响应幅值和系泊张力均符合工程要求,且能改善平台运动性能。

FSRU码头系泊模型实验与数值模拟研究

FSRU在恶劣环境条件下的作业和安全停靠性能与系泊缆张力、靠垫挤压应力、船体6自由度运动等参数有关。针对FSRU码头处海洋环境条件,进行FSRU不同装载状况的模型实验,获得FSRU的6自由度运动及其系泊载荷的动力特性。基于三维辐射和绕射理论,使用Sesam软件进行频域计算,以此为基础在相应海洋环境条件下进行时域耦合分析,获得FSRU 6自由度运动、系泊载荷、靠垫应力等参数的响应时历。结果表明:30%装载、横浪条件下FSRU的运动响应最大,系泊缆张力未达到破断值,靠垫压力超过其压缩60%时的载荷;模型实验对FSRU运动响应和系泊缆张力的预测结果可信,靠垫受力情况需要数值仿真进行辅助研究。

LNG旁靠FSRU码头系泊的水动力性能试验研究

本文对码头系泊的FSRU和LNG船的水动力性能进行了研究,分别对FSRU单船码头和FSRU-LNGC并排码头系泊进行了模型试验。码头与船和船与船之间均采用系泊缆和靠垫进行连接。试验中考虑了风、流、浪等环境因素对码头系泊系统的影响。在风浪流模型试验中,分别测量了不同海况下系泊系统的动态响应,其中包括FSRU和LNG船的六自由度运动响应、系泊缆张力和靠垫接触力。相比较其它浪向,横浪(90°)引起的船舶运动更大,进而导致系泊缆和靠垫的受力增大。结果还表明,FSRU单船码头系泊在所有海况下安全性较好,但对于LNG船旁靠FSRU码头系泊系统,其对环境的响应非常敏感,尤其是横浪环境。

S-spar平台垂荡板数目确定及立管系泊系统耦合分析

考虑到目前S-spar平台垂荡板数目是参考Truss Spar平台3块垂荡板的设计,而未结合平台本身特性进行深入研究,因此基于SESAM对S-spar平台进行频域分析,确定S-spar平台采用4块垂荡板更为合适。在4块垂荡板的S-spar平台频域分析的基础上,对系泊系统及立管进行耦合分析,对比有无立管情况,发现考虑立管后平台各自由度上运动显著减小。为解决立管张力过大的问题,在立管上安装浮子,讨论浮子位置、浮子浮力对立管张力的影响,确定安装500 k N的浮子在距立管悬垂段距顶端65%处为最优方案。

Dynamic Coupled Analysis of the Floating Platform Using the Asynchronous Coupling Algorithm

This paper discusses the numerical modeling of the dynamic coupled analysis of the floating platform and mooring/risers using the asynchronous coupling algorithm with the purpose to improve the computational efficiency when multiple lines are connected to the platform. The numerical model of the platform motion simulation in wave is presented. Additionally, how the asynchronous coupling algorithm is implemented during the dynamic coupling analysis is introduced. Through a comparison of the numerical results of our developed model with commercial software for a SPAR platform, the developed numerical model is checked and validated.

锚链预张力对FDPSO运动响应的影响

作为一种综合性浮式平台,浮式钻井生产储油船简称FDPSO,具备石油钻探、生产、储备等功能,是在浮式生产储油船的基础上发展而来。FDPSO主要工作于海况比较恶劣的深水海域,因而如何准确预报FDPSO的运动响应和锚链的预张力非常必要。本文基于时域耦合方法对FDPSO运动响应和锚链的预张力进行预报,在此基础上将数值结果与试验结果进行对比以验证理论计算的可靠性。通过改变锚链线的预张力来研究预张力对FDPSO运动响应的影响。文中提供了运动响应的时历曲线和响应谱,并对比分析其中的异同,结果表明锚链预张力对纵荡、横荡和横摇运动的响应影响比较大。

Hydrodynamic Analysis of a Semi-submersible Wind-Tidal Combined Power Generation Device

Energy shortages and environmental pollution are becoming increasingly severe globally. The exploitation and utilization of renewable energy have become an effective way to alleviate these problems. To improve power production capacity, power output quality, and cost effectiveness, comprehensive marine energy utilization has become an inevitable trend in marine energy development. Based on a semi-submersible wind-tidal combined power generation device,a three-dimensional frequency domain potential flow theory is used to study the hydrodynamic performance of such a device. For this study, the RAOs and hydrodynamic coefficients of the floating carrier platform to the regular wave were obtained. The influence of the tidal turbine on the platform in terms of frequency domain was considered as added mass and damping. The direct load of the tidal turbine was obtained by CFX.FORTRAN software was used for the second development of adaptive query workload aware software, which can include the external force. The motion response of the platform to the irregular wave and the tension of the mooring line were calculated under the limiting condition(one mooring line breakage). The results showed that the motion response of the carrier to the surge and sway direction is more intense, but the swing amplitude is within the acceptable range. Even in the worst case scenario, the balance position of the platform was still in the positioning range, which met the requirements of the working sea area. The safety factor of the mooring line tension also complied with the requirements of the design specification. Therefore, it was found that the hydrodynamic performance and motion responses of a semi-submersible wind-tidal combined power generation device can meet the power generation requirements under all design conditions, and the device presents a reliable power generation system.

Dynamic Analysis for the Global Performance of An SPM-Feeder-Cage System Under Waves and Currents

In the present study, the dynamic response of a coupled SPM-feeder-cage system under irregular waves and shear currents is analyzed. A numerical model is developed by using the commercial software Orca Flex. Hydrodynamics coefficients of the vessel are calculated by using a 3D diffraction/radiation panel program. First- and second-order wave forces are included in the calculations. Morison equation is used to compute the drag force on line elements representing the net. Drag coefficients are determined at every time step in the simulation considering the relative normal velocity between the structural elements and the fluid flow. The dynamic response of the coupled system is analyzed for various environments and net materials. The results of the study show the effects of solidity ratio of the net and vertical positions of the cage on the overall dynamic response of the system, confirming the viability of this type of configuration for future development of offshore aquaculture in deep waters.

球罐型FSRU系泊布置设计与研究

由于球罐型浮式储存和再气化装置(FSRU)的干舷较高,导致侧向风力通常比同等排水量船舶大,因此系泊设计是该型FSRU设计的重点和难点。文章以某球罐型FSRU为研究对象,对FSRU的系泊系统进行布置设计和系泊分析,保证恶劣海况下FSRU在码头长期系泊的安全。

超长尺度浮式防波堤多模块耦合动力响应分析

为研究多模块浮式防波堤模块之间的耦合动力响应规律,基于目标海域环境条件,提出一种能够提供特大掩护水域的超长尺度浮式防波堤总布置设计方案,并对超长尺度浮式防波堤的构型、连接结构及系泊系统进行设计。在此基础上,基于三维势流理论对超长尺度浮式防波堤的水动力性能进行频域和时域分析,考虑环境载荷作用下浮式防波堤多模块耦合运动,并对其中间及两侧模块的运动响应及系泊缆张力进行对比分析。研究结果表明:横浪和斜浪工况下,超长尺度浮式防波堤中间模块在垂荡、横摇和纵摇方向上的运动均最剧烈。由于防波堤首部模块在横浪和斜浪工况下横荡运动最剧烈,因此浮式防波堤首部模块迎浪运动侧系泊缆在2种工况下所受张力最大,这在超长尺度浮式防波堤系泊系统设计过程中需重点关注。数值模拟结果可为此后超长尺度浮式防波堤设计及工程化应用提供技术支撑。