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1.
Hybrid model testing technique is widely used in verification of a deepwater floating structure and its mooring system,but the design of the truncated mooring systems which can reproduce both static and dynamic response same as the full-depth mooring system is still a big challenge,especially for the mooting systems with large truncation.A Cell-Tress Spar operated in 1500 m water depth is verified in a wave basin with 4 m water depth.A large truncation factor arises even though a small model scale 1:100 is adopted.Computer program modules for analyzing the static and frequency domain dynamic response of mooting line are combined with multi-objective genetic algorithm NSGA-II to optimize the truncared mooting system.Considering the asymmetry of layout of mooring hnes,two different truncated mooring systems are respectively designed for both directions in which the restoring forces of the.mooting system are quite,different.Not only the static characteristics of the mooting systems are calibrated,but also the dynamic responses of the single truncated mooting line are evaluated through time domain numerical simulation and model tests.The model test results of 100-year storm in the GOM are reconstructed and extrapolated to a full depth.It is found that the experimental and numerical resuits of Spar wave frequency motion agree well,and the dynamic responses of the full-depth mooring lines are better reproduced,but the low frequency surge motion is overestimated due to the smaller mooring-induced damping.It is a feasible method adopting different truncated mooring systems for different directions in which the restoring force characteristics are quite different and cannot be simulated by one truncated mooring system.Hybrid verification of a deepwater platform in wave basin with shallow water depth is still feasible if the truncated mooring systems are properly designed,and numerical extrapolation is necessary. 相似文献
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Dynamic Response Analysis of the Equivalent Water Depth Truncated Point of the Catenary Mooring Line
The real-time computer-controlled actuators are used to connect the truncated parts of moorings and risers in the active hybrid model testing system. This must be able to work in model-scale real time, based on feedback input from the floater motions. Thus, mooring line dynamics and damping effects are artificially simulated in real time, based on a computer-based model of the problem. In consideration of the nonlinear characteristics of the sea platform catenary mooring line, the equations of the mooring line motion are formulated by using the lumped-mass method and the dynamic response of several points on the mooring line is investigated by the time and frequency domain analysis method. The dynamic response of the representative point on the mooring line is analyzed under the condition of two different corresponding upper endpoint movements namely sine wave excitation and random wave excitation. The corresponding laws of the dynamic response between the equivalent water depth truncated points at different locations and the upper endpoint are obtained, which can provide technical support for further study of the active hybrid model test. 相似文献
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The model test method of the FPSO and offloading system is investigated by using the development mode of “FPSO + CALM + TANKER” working in a 1700-m depth of offshore West Africa. An equivalent design based on static and dynamic similarity criteria for oil offloading line (OOL) is discussed, and a type of creative method for the equivalent design of OOL in a model test is proposed. Based on the static similarity criterion, the truncated design of the FPSO mooring system in water depth and horizontal directions is carried out. After that, a relevant static optimization is conducted. Meanwhile, to avoid interference between the FPSO mooring system and CALM mooring system, a horizontal equivalent design for the CALM mooring system is provided. On this basis, the model test scheme is conducted. Time domain coupled analyses for the whole system before and after truncation are later performed. After comparison, it is observed that the calculated results of the truncated system are basically consistent with those of the prototype system, and the design of the model test scheme is demonstrated to be robust and reliable. 相似文献
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Impact Analysis of Air Gap Motion with Respect to Parameters of Mooring System for Floating Platform
In this paper, the impact analysis of air gap concerning the parameters of mooring system for the semi-submersible platform is conducted. It is challenging to simulate the wave, current and wind loads of a platform based on a model test simultaneously. Furthermore, the dynamic equivalence between the truncated and full-depth mooring system is still a tuff work. However, the wind and current loads can be tested accurately in wind tunnel model. Furthermore, the wave can be simulated accurately in wave tank test. The full-scale mooring system and the all environment loads can be simulated accurately by using the numerical model based on the model tests simultaneously. In this paper, the air gap response of a floating platform is calculated based on the results of tunnel test and wave tank. Meanwhile, full-scale mooring system, the wind, wave and current load can be considered simultaneously. In addition, a numerical model of the platform is tuned and validated by ANSYS AQWA according to the model test results. With the support of the tuned numerical model, seventeen simulation cases about the presented platform are considered to study the wave, wind, and current loads simultaneously. Then, the impact analysis studies of air gap motion regarding the length, elasticity, and type of the mooring line are performed in the time domain under the beam wave, head wave, and oblique wave conditions. 相似文献
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Effect of Failure Mode of Taut Mooring System on the Dynamic Response of A Semi-Submersible Platform
Mooring system failure can lead to largely different dynamic response of floating structures when compared to the response under the condition of intact mooring system. For a semi-submersible platform with taut mooring system under extreme environmental conditions, the typical mooring system failure includes anchor line breaking failure due to the broken anchor line, and the anchor dragging failure caused by the anchor failure in the seabed soil due to the shortage of the anchor bearing capacity. However, study on the mooring failure caused by anchor failure is rare. The current work investigates the effect of three failure modes of taut mooring system on dynamic response of a semi-submersible platform, including one line breaking failure, two lines breaking failure, and one line breaking with one line attached anchor dragging failure. The nonlinear polynomial mooring line model in AQWA was used with integrating the load and displacement curve from the anchor pulling study to characterize the anchor dragging behavior for mooring system failure caused by the anchor failure. The offsets of the platform and the tension of mooring lines were analyzed for mooring system failure with 100-year return period. It is found that the mooring failure of one line breaking with one line attached anchor dragging is a case between the other two mooring failures. The traditional mooring analysis considering only the damaged condition with one line breaking is not safe enough. And the simple way of mooring analysis of two lines breaking is too conservative for the costly offshore engineering.
相似文献8.
Dynamics of large-truncated mooring systems coupled with a catenary moored semi-submersible 总被引：2，自引：2，他引：0
With the floating structures pushing their activities to the ultra-deep water,model tests have presented a challenge due to the limitation of the existing wave basins.Therefore,the concept of truncated mooring system is implemented to replace the full depth mooring system in the model tests,which aims to have the same dynamic responses as the full depth system.The truncated mooring system plays such a significant role that extra attention should be paid to the mooring systems with large truncation factor.Three different types of large truncation factor mooring system are being employed in the simulations,including the homogenously truncated mooring system,non-homogenously truncated mooring system and simplified truncated mooring system.A catenary moored semi-submersible operating at 1000 m water depth is presented.In addition,truncated mooring systems are proposed at the truncated water depth of 200 m.In order to explore the applicability of these truncated mooring systems,numerical simulations of the platform’s surge free decay interacting with three different styles of truncated mooring systems are studied in calm water.Furthermore,the mooring-induced damping of the truncated mooring systems is simulated in the regular wave.Finally,the platform motion responses and mooring line dynamics are simulated in irregular wave.All these simulations are implemented by employing full time domain coupled dynamic analysis,and the results are compared with those of the full depth simulations in the same cases.The results show that the mooring-induced damping plays a significant role in platform motion responses,and all truncated mooring systems are suitable for model tests with appropriate truncated mooring line diameters.However,a large diameter is needed for simplified truncated mooring lines.The suggestions are given to the selection of truncated mooring system for different situations as well as to the truncated mooring design criteria. 相似文献
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等效水深截断是混合模型试验中非常重要的一步,合理的截断方案是模型试验成功的前提。现有的研究大多忽略对平台转动的考虑,该文在静态相似准则的基础上增加对平台转动的考虑,推导了系泊系统回复力和转矩的计算公式,建立了满足静态一致性的目标函数,进而采用粒子群算法进行等效水深截断优化设计。以某深水半潜式平台为例,首先在不考虑转动的情况下对其系泊系统进行等效截断,研究发现截断水深的变化对转矩的优化结果影响较大,从而证明了平台转动是应该考虑的。其次在考虑转动的情况下对系泊系统进行等效截断,通过水动力软件验证所优化的结果,证明该方法的可行性,为后续的等效水深截断优化设计的研究提供参考。 相似文献
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我国的边际油田大多年产量小且开发年限短，周围没有可依托设施的油田。针对此情况，可采用“蜜蜂式”开发模式。针对浸没式可移动外输终端这一新型概念设计，选取关键工况开展了时域耦合分析，研究了系泊系统参数对可移动外输终端最大水平位移和系泊缆最大张力的影响。以可移动外输终端最大水平位移和系泊缆最大张力最小为优化目标，以系泊缆结构安全为约束条件，构建了系泊系统多目标优化模型。分别建立了基于NSGA-Ⅱ和多目标粒子群算法的系泊系统优化框架，并应用这两种算法对系泊系统进行了优化设计。结果表明，NSGA-Ⅱ和多目标粒子群算法均可以解决系泊系统多目标优化问题，粒子群算法优化速度快，但通过NSGA-Ⅱ得到的Pareto前沿优化性能更好，因此更适合开展浸没式可移动外输终端的系泊系统优化。 相似文献
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Optimal Design of Equivalent Water Depth Truncated Mooring System Based on Baton Pattern Simulated Annealing Algorithm简 总被引：2，自引：2，他引：0
The highest similarity degree of static characteristics including both horizontal and vertical restoring force-displacement characteristics of total mooring system, as well as the tension-displacement characteristics of the representative single mooring line between the truncated and full depth system are obtained by annealing simulation algorithm for hybrid discrete variables （ASFHDV, in short）. A“baton” optimization approach is proposed by utilizing ASFHDV. After each baton of optimization, if a few dimensional variables reach the upper or lower limit, the boundary of certain dimensional variables shall be expanded. In consideration of the experimental requirements, the length of the upper mooring line should not be smaller than 8 m, and the diameter of the anchor chain on the bottom should be larger than 0.03 m. A 100000 t turret mooring FPSO in the water depth of 304 m, with the truncated water depth being 76 m, is taken as an example of equivalent water depth truncated mooring system optimal design and calculation, and is performed to obtain the conformation parameters of the truncated mooring system. The numerical results indicate that the present truncated mooring system design is successful and effective. 相似文献
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Hydrodynamic performance of an ultra deep turret-moored Floating Liquefied Natural Gas(FLNG) system is investigated.Hydrodynamic modeling of a turret-moored FLNG system,in consideration of the coupling effects of the vessel and its mooring lines,has been addressed in details.Based on the boundary element method,a 3-D panel model of the FLNG vessel and the related free water surface model are established,and the first-order and second-order mean-drift wave loads and other hydrodynamic coefficients are calculated.A systematic model test program consisting of the white noise wave test,offset test and irregular wave test combined with current and wind,etc.is performed to verify the numerical model.Owing to the depth limit of the water basin,the model test is carried out for the hydrodynamics of the FLNG coupled with only the truncated mooring system.The numerical simulation model features well the hydrodynamic performance of the FLNG system obtained from the model tests.The hydrodynamic characteristics presented in both the numerical simulations and the physical model tests would serve as the guidance for the ongoing project of FLNG system. 相似文献
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Yoji Ogawa 《Applied Ocean Research》1984,6(3):140-147
The integrated equations of deep sea mooring lines in static equilibrium under consideration of gravity force and line elongation are obtained. The most useful forms of the equations for designing deep sea mooring system are those in which horizontal displacement and horizontal and vertical components of tension are obtained as functions of line length, water depth, critical tension and unit weight of line.When the dynamic simulation of a buoy system is carried out, line tensions acting on the buoy should be represented as a linear function of displacement. Therefore the linearisation method is introduced by use of linearisation coefficient matrix. Translation formulae for the matrix from two to three dimensions is also presented.The influence of line elongation on the horizontal component of tension in a taut mooring condition is important, therefore the elongation of stretched deep sea mooring line must be considered carefully. Also, the scaling law under consideration of line elongation in static equilibrium, which is necessary in estimation from a small sized experiment, is discussed. 相似文献
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采用集中质量法研究了绷紧式系泊系统中系缆由于松弛-张紧过程产生的冲击张力。建立系泊缆绳离散的集中质量模型,对其独立单元进行受力分析并建立了单元的运动方程。给定缆绳上端点简谐激励,通过Ansys中的Aqwa模块,分析了缆绳的运动响应;针对缆绳运动响应过程中的三种状态进行了模拟计算,探讨了冲击张力产生的条件;研究了缆绳初始预张力、上端点激励幅值和频率、拖曳力系数、弹性模量以及单位长度质量对动态张力的影响。研究结果表明:这些影响因素不仅会影响缆绳动态张力的大小,也会对缆绳中的冲击张力产生一定的影响。 相似文献
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具有链—缆—链结构的复合系泊链缆因其相对于全钢链质量和成本上的优势而在深水系泊中得以广泛应用。基于细长杆理论采用有限差分法建立了可以考虑链—缆—链结构的复合系泊缆数值模型,将其应用于不同工况下全钢链和复合链缆运动的数值模拟中,并开展了验证。首先,将单根钢链顶张力数值模拟结果与不同工况下的模型试验结果进行了对比,验证了数值预报程序应用于全钢链的准确性。然后,对于复合系泊链缆开展了静刚度和动刚度迭代数值模拟,并将模拟结果同已发表文章中的算例结果进行比较,验证了该数值模型在复合链缆模拟上的准确性。发现对于单根钢锚链的验证,激励半径越大,激励周期越小,一个周期内顶张力幅值及其极差越大,钢链运动就越剧烈。对于链—缆—链式复合系泊链缆的验证,发现静刚度迭代中数值模拟结果与算例结果差异较小;对于动刚度迭代,除个别大幅慢漂工况外,两者有较高的吻合;且激励周期越小,激励半径越大,复合系泊链缆顶张力越大,弹性模量越小,运动越剧烈。对于聚酯缆刚度的敏感性分析,发现改变动刚度经验公式参数的情况下,杨氏模量的静刚度迭代和动刚度迭代结果误差分别最大达到了60.81%和68.21%,因此合成纤维材料特性对复合系泊链... 相似文献
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The present work reports a Hybrid Modular Floating Structure (HMFS) system with typical malfunction conditions. The effects of both fractured mooring lines and failed connectors on main hydrodynamic responses (mooring line tensions, module motions, connector loads and wave power production) of the HMFS system under typical sea conditions are comparatively investigated. The results indicate that the mooring tension distribution, certain module motions (surge, sway and yaw) and connector loads (Mz) are significantly influenced by mooring line fractures. The adjacent mooring line of the fractured line on the upstream side suffers the largest tension among the remaining mooring lines, and the case with two fractured mooring lines in the same group on the upstream side is the most dangerous among all cases of two-line failures in view of mooring line tensions, module motions and connector loads. Therefore, one emergency strategy with appropriate relaxation of a proper mooring line has been proposed and proved effective to reduce the risk of more progressive mooring line fractures. In addition, connector failures substantially affect certain module motions (heave and pitch), certain connector loads (Fz and My) and wave power production. The present work can be helpful and instructive for studies on malfunction conditions of modular floating structure (MFS) systems.
相似文献18.
Failure of net cage and mooring system is of great concern to the marine aquaculture industry. To avoid the structure failure in storm waves and current during typhoon events, net cage can submerge below the water surface in practice. A submersible net cage and mooring system is analyzed by numerical simulation and physical model test. The numerical model is established based on the lumped mass method and principle of rigid body kinematics. A series of physical model tests are conducted to validate the numerical model of single net cage and grid mooring system in waves and current. Numerical results correspond well with data obtained from physical model test. The results indicate that when net cage is submerged below the water surface, the deformation of net cage in waves can be improved significantly, and the tension force on the anchor line, bridle line and grid line will decrease significantly. However, the tension force on the buoy line in the submergence condition is larger than that in the floating condition. Different relative submergence ratios are also considered in our numerical simulation, and a relative submergence ratio equal to 0.1 is suggested here. The tension reduction ratio (56%) for the four-cage system is larger than that for the single-cage (52%) and double-cage systems (44%). 相似文献
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从提高锚泊系统收放时效性入手,提出了一种半潜式钻井平台复合式锚泊系统组分配比优化设计方法,旨在尽可能降低复合式锚泊系统的钢链配比长度,提高收放效率。结合锚泊系统设计参数,制定优化设计准则,建立优化分析流程,采用ANSYS-AQWA建立锚泊定位半潜式平台水动力分析模型,获得平台运动参数和锚链动力参数,对平台漂移量、锚链最小安全系数、走锚临界张力、锚链最小卧底长度和起锚力进行无量纲指标分析,并综合考虑张力倾角与预张力对优化结果的影响,获得复合式锚泊系统钢链与钢缆的最优配比关系,确定最优钢链长度为395 m,较原钢链长度缩短225 m,钢链收放时间降低36%,进一步提高锚泊系统收放时效性,并降低平台可变荷载。 相似文献
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由于聚酯缆绳具备优异的力学性能,促使以其为主体系缆的绷紧式系泊系统得以广泛应用和发展。但聚酯系缆具有复杂的黏弹性和黏塑性,且由于在安装和使用过程中可能产生不同程度的损伤,使得聚酯系缆的动刚度特性发生演变,从而对系泊系统的动力响应产生直接影响。以一系泊于1 020 m水深的Spar平台为例,运用ABAQUS软件建立了由聚酯缆绳组成的系泊系统有限元模型,并利用ABAQUS子程序将损伤缆绳动刚度经验公式进行导入计算,以更好地反映系缆真实的动刚度变化。基于该有限元模型,计算了在相同水流、波浪工况下,不同损伤度、不同损伤系缆的系缆张力历程和平台的横荡、纵荡位移响应,分析了不同损伤度、不同损伤系缆对系缆张力及平台位移的影响。这些成果对把握绷紧式系泊系统在聚酯系缆有损伤情况下的非线性动力响应及其安全应用具有重要的参考价值。 相似文献