共查询到18条相似文献，搜索用时 125 毫秒
1.
吸力锚基础锚泊线准静力分析模型 总被引：2，自引：0，他引：2
随着海洋工程中吸力锚基础尺寸的增大,在系泊系统设计时必须考虑锚泊线切入土体段对整体设计的影响.建立了一种新的基于坐标轴划分微段的准静力分析模型,该模型包括锚泊线切入土体段与水中悬浮段两部分,无需给定锚泊线的初始长度.计算预张状态和工作条件下的锚泊线构形与张力分布,得到锚泊线顶端张力与浮体水平偏移特性曲线,分别对不同预张力和布置沉子对锚泊线状态的影响进行研究,并分析考虑锚泊线切入土体段的必要性. 相似文献
2.
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
3.
以三锚系浮标系统为研究对象,基于AQWA与OrcaFlex软件开展了三锚系大型浮标系统运动响应特性数值模拟研究。对直径10 m的浮标结构在波浪荷载下的水动力特性进行研究,校核了浮标的初稳性和大倾角稳性特征,计算分析了浮标的附加质量、辐射阻尼、运动响应幅值算子RAO等水动力参数,阐明了不同风、浪、流工况下三锚系浮标与辅助浮筒的运动响应特性,揭示了浮标三锚链导缆孔处锚泊张力随入射角度、波高和周期等的变化规律。研究结果表明：该浮标稳性和随波性能较好。与无浮筒三锚系浮标相比,带辅助浮筒的三锚系浮标系统的运动响应和锚泊张力减小,随着波高和周期增大,三锚系浮标系泊锚链的极端张力值逐渐增大,尤其是在极端海况下,迎浪向锚链极端张力急剧增大。 相似文献
4.
深水悬链锚泊线既为上部浮体运动提供恢复力,同时也提供阻尼力,其中阻尼力主要是由于上部浮体运动牵动悬链锚泊线局部振动和整体运动耗散能量而形成的拖曳粘性阻尼力.利用单根锚泊线由于上部浮体运动而吸收的能量来计算锚泊线的拖曳粘性阻尼.锚泊线和海床之间的接触作用基于刚性海床假定,利用Morrison公式计算锚泊线的惯性力和拖曳力荷载.用有限元方法进行非线性时域动力分析,分别计算静水条件和考虑流速分布两种工况下,上部浮体发生慢漂运动、波频运动以及两者组合运动时的锚泊线动力响应,比较不同工况下锚泊线的最大张力和粘性阻尼. 相似文献
5.
基于三维频域势流理论,计算船体的水动力参数;采用动态耦合方法分析了深海半潜式生产平台各系统之间的相互作用特征,研究了立管系统对锚泊系统定位能力的影响。计算结果表明,立管系统在一定程度上增加了整个系统的刚度,其所受的附加质量和阻尼可降低平台的低频响应,从而降低平台的偏移和系泊缆的张力;海流将增大立管上的拖曳力,使平台偏移更远,锚索上的张力更大;立管系统对锚泊系统定位性能的最终影响需综合考虑多种因素的叠加。对目标平台而言,由于服役海域的流速较大,对立管的拖曳作用较为明显。因此,为确保平台的安全性,当服役海域流速较大时,带有多立管的平台,其锚泊系统的设计应考虑立管的影响。 相似文献
6.
以新型激光雷达浮标系统为研究对象,基于ANSYS/AQWA开展了激光雷达浮标系统运动响应特性数值研究,研究了浮标吃水深度、形状参数对于激光雷达浮标运动响应的影响规律,分析了附加质量、辐射阻尼、运动响应RAO及一阶、二阶波浪力等水动力参数。采用时域分析方法对不同风浪流荷载入射角度下的激光雷达浮标锚泊系统张力特性进行了计算分析。研究结果表明:随着浮标吃水深度的增加,浮标纵荡方向响应无明显变化,垂荡响应显著增大;随着浮标底部圆台直径的增大,浮标纵荡方向响应变化较小,而圆柱形浮标垂荡运动响应显著大于圆台形浮标;当浮标系泊锚链发生松弛—张紧状态变化时易出现极端张力,且极端张力出现的幅值和频率随有效波高的增大和谱峰周期的减小而增大。 相似文献
7.
法向承力锚(Vertically Loaded Plate Anchor,VLA)是一种适用于深水的新型系泊基础,它的拖曳安装过程直接决定了其系泊定位的精度和锚体的最终承载能力。综合考虑VLA锚体、锚泊线和上部船体的运动,建立了一种新的准静力整体分析模型。模型包括不断贯入海床的锚体、锚泊线(土中反悬链段和水中悬链段)和安装船体三部分,针对确定的锚泊线长度,安装船运动张紧锚泊线进行安装的过程,计算了此过程中锚体的运动轨迹、锚泊线形态和作用在船体上的锚泊线张力矢量的变化,重点分析了不同抛链长度和海床土体的参数对安装过程控制的影响,发现链长与水深之比达到5时,接近极限贯入深度。 相似文献
8.
为研究松弛-张紧现象对串联浮筒多组分锚泊线的影响以及规律,本文对其松弛-张紧特性进行了数值模拟分析。基于向量式有限元(VFIFE)方法,建立了以锚链-锚缆-锚链多段锚泊线和浮筒组合而成的多组分锚泊线动力学分析模型,研究了串联浮筒多组分锚泊线的松弛-张紧特性。在顶端水平预张力为定值的条件下,通过改变顶端纵荡激励的振幅和频率以及浮筒的浮重、位置和数量,预测串联浮筒多组分锚泊线的松弛-张紧现象发生的条件以及规律。结果表明,通过控制顶端激励的频率和振幅以及浮筒的浮重、位置和数量,可以有效降低松弛-张紧现象的发生,降低串联浮筒多组分锚泊线断裂的风险。 相似文献
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10.
海上浮式风力机受风、浪、流等外部载荷影响,运营期间经常处于偏航工况,给风力机基础运动响应和锚泊载荷带来重要影响.基于经典叶素动量理论及势流理论,建立海上浮式风力机水—气动力耦合分析模型,对在非定常风、不规则波浪联合作用下,风力机偏航时基础运动响应及锚泊载荷等进行分析.研究发现,额定风速工况下,风力机偏航对平台纵荡和纵摇运动影响较大,偏航30°时纵荡和纵摇平均值比偏航0°时分别下降20.68％和37.36％,垂荡运动响应受风力机偏航影响较小;锚泊载荷变化趋势与平台运动及锚链布置有关,平台纵荡对锚泊载荷影响较大,偏航30°时锚链#1有效张力平均值比偏航0°时下降12.98％. 相似文献
11.
Fish cages in the open sea are exposed to cycle loads due to irregular wave climate during their service life, and thus the fatigue reliability assessment of mooring system should be conducted to ensure the safe operation. The aim of this study is to evaluate the fatigue failure probability of mooring system for fish cage. Numerical simulation of net cage in random waves is performed and the time dependent approach is applied to conduct the fatigue reliability analysis of shackle chains based on S-N curve method. The sensitivity analysis of fatigue reliability of mooring line to the uncertainty of random variables in the fatigue limit state is conducted. In addition, the system reliability for mooring system is analyzed and the effect of the initial pretension and safety factor on system reliability is investigated. The results indicate that a case without the initial pretension on anchor lines is helpful to decrease the failure probability of mooring system and the safety factor of mooring lines in the current regulation is conservative for the system reliability against fatigue damage. 相似文献
12.
This work presents the development of Artificial Neural Networks for the analysis of any arbitrarily defined spread-mooring configuration for floating production systems (FPS), considering a given scenario characterized by the water depth, metocean data, characteristics of the platform hull, and the riser layout. The methodology is applied to recent designs of deepwater semi-submersible platforms connected to a large number of risers with asymmetrical layout. In such cases, the design variables may include values for the azimuthal spacing and mooring radius varying along the corners of the platform, besides the pretension and material of the lines. The results of the case study indicated that, given any mooring configuration characterized by the combination of all these design variables, the ANNs provide fairly accurate values for the parameters of the response that are required for the design of mooring systems (typically platform offsets and line tensions). 相似文献
13.
The drag-induced damping in a mooring cable due to combined first- and second-order wave excited motion of a moored vessel has been determined by statistical linearisation. A dynamic stiffness approach developed elsewhere is used to deal with the dynamics of the mooring cables. The power spectral densities of low- and wave-frequency responses are obtained which clearly show the influence of mooring line damping. The non-Gaussian probability density functions (pdf) and expected crossing rates of vessel responses and dynamic cable tensions are determined using the Kac–Seigert technique, and the influence of drag damping is highlighted. 相似文献
14.
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
15.
The motion response prediction of offshore structures may be carried out using time domain or frequency domain models or model tests. The frequency domain analysis uses the simplified, linearised form of the motion equations and it is very economical. The time domain analysis, unlike frequency domain models, is adequate to deal with non-linearities such as viscous damping and mooring forces, but it requires sophisticated solution techniques and it is expensive to employ. For moored semisubmersibles time domain techniques must be employed since there are strong nonlinearities in the system due to mooring line stiffness and damping and viscous drag forces. In the first part of this paper a time domain model to predict the dynamic response of a semi-submersibles are developed and the effect of thrusters and mooring line damping are incorporated into the time domain model. In the second part time domain simulations are carried out to find the total extreme motions and mooring forces. 相似文献
16.
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 te... 相似文献
17.
Hull/mooring/riser coupled dynamic analysis and sensitivity study of a tanker-based FPSO 总被引：2，自引：0，他引：2
A computer program is developed for hull/mooring/riser coupled dynamic analysis of a tanker-based turret-moored FPSO (Floating Production Storage and Offloading) in waves, winds, and currents. In this computer program, the floating body is modeled as a rigid body with six degrees of freedom. The first- and second-order wave forces, added mass, and radiation damping at various yaw angles are calculated from the second-order diffraction/radiation panel program WAMIT. The wind and current forces for various yaw angles of FPSO are modeled following the empirical method suggested by OCIMF (Oil Company International Marine Forum).
The mooring/riser dynamics are modeled using a rod theory and finite element method (FEM), with the governing equations described in a generalized coordinate system. The dynamics of hull, mooring lines, and risers are solved simultaneously at each time step in a combined matrix for the specified connection condition. For illustration, semi-taut chain-steel wire-chain mooring lines and steel catenary risers are employed and their effects on global FPSO hull motions are investigated. To better understand the physics related to the motion characteristics of a turret-moored FPSO, the role of various hydrodynamic contributions is analyzed and assessed including the effects of hull and mooring/riser viscous damping, second-order difference-frequency wave-force quadratic transfer functions, and yaw-angle dependent wave forces and hydrodynamic coefficients. To see the effects of hull and mooring/riser coupling and mooring/riser damping more clearly, the case with no drag forces on those slender members is also investigated. The numerical results are compared with MARIN's wave basin experiments. 相似文献
18.
《Ocean Engineering》1999,26(2):125-145
This paper presents results from a full scale decay test made with a tanker in a relatively protected area in the Brazilian coast. In at least two tests the environmental loads (wind, waves and current) were very small and the time history of the surge motion was well behaved, making it possible to check some proposed models for the damping in the hull and mooring lines. Field data seem to confirm that the damping is indeed of the fluid viscosity type and the theoretical models are able to recover roughly 75% of the observed damping, the energy dissipation in the mooring lines being, by far, the major contribution. The remaining 25% are likely due to non modeled effects, such as the environment influence, which although small and not measured certainly exists, and to the friction between the mooring lines and the seabed. 相似文献