深水钢悬链线立管非线性动力分析

钢悬链线立管是近年来国内外发展起来的一种新型深水立管系统,由于成本低、对浮体运动有较大适应性,且耐高温高压环境而受到广泛关注。本文主要对钢悬链线立管的运动进行了时域模拟,采用三维集中质量法建立了深海立管模型,考虑重力、浮力、流体拖曳力、张力、惯性力、剪切、弯曲刚度及海床作用的影响。分别用Newton-Raphson和Newmark-β数值方法求解立管的静态、动态特性。主要分析了钢悬链线立管的构型、张力、剪力和弯矩特性,分析了系缆在顶端不同幅值不同频率激励下疲劳特征点的有效张力变化趋势,对比分析了剪切、弯曲刚度对钢悬链立管顶端张力产生的影响。     

深水钢悬链立管弃管回收技术研究

阐述深水钢悬链立管安装中的弃管回收工艺,采用理论分析和数值分析相结合的方法,对深水钢悬链立管安装中的弃管回收进行分析.基于经典悬链线理论,编制钢悬链立管弃管回收分析软件SCRCOV,针对1500m水深和10 in SCR制定弃管回收方案,经商业软件ORCAFLEX验证,自编软件计算结果是准确的.     

深水悬链线式柔性立管参数敏感性分析

针对柔性立管所处的深水环境,选取应用较为广泛的悬链线式布置方法,在特定的海洋环境中,在大型有限元软件OrcaFlex上建立悬链线立管模型进行动力分析。选取悬挂角、立管末端锚固点位置和管内流体等关键参数进行参数敏感性分析。结果表明:悬挂角的变化对立管顶部曲率有作用,但立管底部曲率和最大张力对悬挂角的变化不敏感;立管末端锚固点位置变化对立管动力响应有明显影响,布置立管时需重点考虑;立管曲率和弯矩对管内流体密度及流速的变化不敏感,但立管最大张力随管内流体密度的增大而减小,随管内流速的增大而增大。     

深水SCR立管触地区域管土作用研究进展(英文)

钢悬链线立管作为一种全新的深水立管系统已经在国外多个项目中应用,总结了有关深水钢悬链线立管触地区域管土相互作用的研究进展,主要包括STRIDE和CAluSIMA工业合作计划的研究数据和其他的相关论文,能够为国内深水钢悬链线立管的研究提供参考.     

深水缓波型刚性立管的设计方法

缓波型刚性悬链线立管由于其良好的力学性能和较低的成本,适用于深水油气田开发。本文详述了缓波型刚性悬链线立管的设计准则和设计流程,给出了分布式浮块的设计方法和等效原则,推导了等效水动力参数的计算公式。通过静力分析,得到了不同浮块的布置位置和浮力系数对立管形态、顶端张力、弯矩分布的影响;通过动力分析,得到了沿管等效应力响应的分布规律,为缓波型刚性悬链线立管的设计提供了有益的参考。     

深水半潜式平台钢悬链立管提升过程模拟分析

针对国内首个半潜式生产平台的钢悬链立管（steel catenary riser,SCR）的安装过程进行研究，给出了适用于半潜式平台的SCR张力转移、提升和就位方案。结合浮式平台和立管布置特点，给出立管提升系统锚链下放点初步位置，并用数值方法对SCR张力转移、提升和就位过程进行模拟。在空管和注水两种工况下给出了SCR顶部张力、立管与旁通最小净距以及立管顶部的倾角，进一步验证了论文提出的安装方案的可行性，同时给出了立管提升系统需要的最大张力，为保障海上施工现场安全提供技术支持。     

深水SOR立管触地区域管土作用研究进展

钢悬链线立管作为一种全新的深水立管系统已经在国外多个项目中应用，总结了有关深水钢悬链线立管触地区域管土相互作用的研究进展，主要包括STRIDE和CARISIMA工业合作计划的研究数据和其他的相关论文，能够为国内深水钢悬链线立管的研究提供参考．     

平台运动下悬链线立管涡激振动响应特性分析

悬链线立管会在半潜平台运动带动下出现涡激振动现象,对立管疲劳寿命造成影响.借助海工结构物动力分析软件Orcaflex建立立管模型,使用Iwan-Blevins尾流振子模型进行数值模拟.通过与试验结果对比验证了该方法的可行性.同时建立实尺度悬链线立管模型,并考虑背景海流的影响,分析平台垂荡、纵荡运动下的立管涡激振动响应和疲劳损伤.研究表明,平台运动产生的非定常流场将引起悬链线立管发生涡激振动现象,并在背景洋流激励的基础上增大疲劳损伤,在立管结构实际工程设计时应予以关注.     

深水钢悬链线立管顺流向非线性动力分析

深水钢悬链线立管在外部流体作用下的动力响应在立管的性能优化设计中是非常重要的.文章考虑了深水钢悬链线立管轴向大应变的特性以及弯曲刚度和内流的影响,利用Hamilton原理和拉格朗日应变理论建立了立管的二维动力学模型.将外部流体的非线性作用力用Morison方程表示,通过Hermite插值函数对动力学方程进行离散,采用平均加速度法求解立管的动力响应.探讨了外部流体的非线性作用力对海洋立管顺流向动力响应的影响以及不同流速和拖曳力系数与海洋立管共振响应幅值的关系.     

管土作用下的钢悬链线立管动力响应及其疲劳分析

钢悬链线立管的疲劳分析得到越来越多的重视,尤其是其与海床土体相互作用引起的疲劳。本文根据Aubeny提出的管土作用模型以及Bridge提出的土体吸力模型,采用有限元方法,在考虑其与海床土体相互作用的基础上,分析了钢悬链线立管在不同载况作用下的动力响应及疲劳损伤。分析发现,钢悬链线立管上触地点和悬挂点处的疲劳损伤更为显著;洋流载荷对立管疲劳损伤的影响随着水深的增加而减弱;土体吸力的存在,会增大触地段尤其是触地点附近的疲劳损伤;立管触地点附近的疲劳损伤与土体刚度呈正相关。     

考虑内流和海床作用的柔性立管和钢悬链线立管非线性分析(英文)

Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.     

台风条件下TLP串行立管系统碰撞分析

TLP立管系统以丛式方阵排列,台风条件下立管在波浪、海流及平台的联合作用下可能发生碰撞,有必要深入研究TLP串行立管系统的碰撞情况。文章基于DNV-RP-F203规范和Huse半经验尾流模型,提出台风条件下串行立管下游立管来流速度计算方法和立管系统碰撞分析方法,建立串行立管—井口—导管系统耦合有限元模型,研究台风条件下串行生产立管系统碰撞时的力学特性,在整体碰撞分析的基础上进行立管局部碰撞精细化分析,对比分析立管局部碰撞理论解和仿真解的不同。结果表明:下游立管来流速度的计算至少采用文中建立的方法迭代3次。串行立管发生碰撞时的最大应力发生在泥面导管处,碰撞位置应力发生了突变;立管发生碰撞的位置在水深100-120 m范围内。立管局部碰撞分析的理论解和仿真解基本吻合。     

Catenary riser sliding and rolling on seabed during induced lateral movement

Catenary risers have an interaction zone with the seabed, usually referenced as flowline. Movements in this region can be induced by sea currents and large offsets in floating unit, leading to touchdown position changes and affecting internal loads along riser length. In this work the contact flowline-seabed is modeled including sliding and rolling friction. Case studies involving large offsets in floating unit and lateral sea currents are solved to better understand the consequences of possible rolling and large sliding. The riser is modeled using a geometrically-exact finite element beam model. The contact is addressed with a new technique to include rotation movements from underlying beam models. This leads to global riser models including complex kinematics, being able to represent scenarios with alternating sliding/rolling and its consequences on internal loads of riser structure. A parametric study is performed to measure the influence of the friction coefficient in tension and torsion along typical flexible pipe and steel pipe catenary risers.     

钢悬链式立管涡激振动疲劳损伤参数分析

针对钢悬链式立管的结构特性,采用了简化后的振动模型。先对立管进行了模态分析;再根据立管的模态特性结合环境水流参数,采用模态叠加法对立管进行了涡激振动疲劳损伤分析。分析过程中,通过改变流速大小、立管壁厚、立管外径、内部介质以及抑制立管涡激振动的螺旋列板长度等参数,对立管的涡激振动疲劳损伤进行了相应的参数分析。结果表明:立管疲劳损伤随水流速度的增大、立管外径的增大以及内部介质密度的降低呈现上升趋势,但是壁厚变化对立管疲劳损伤大小影响却不显著。     

Extreme response based reliability analysis of composite risers for applications in deepwater

As current oil reserves start to deplete, companies are looking to exploit deeper deposits. At these greater depths composite risers, with their high strength-to-weight ratio, reduce the effective tensions and bending moments compared to steel risers. However, there is still limited research into their behaviour, with one key missing element being a comparison with traditional riser designs which accounts for variances in material properties and wave loads. This paper therefore conducts a strength-based reliability analysis of composite catenary risers operating between 1,500 m and 4,000 m. A static global catenary model is combined with Classical Laminate Theory to determine the extreme response and its performance is verified against FEA. This response is evaluated with the Tsai-Wu failure criterion to determine first-ply failure. The effect of laminate moisture absorption on the long-term reliability of submerged composite-based risers is also investigated as it can cause a significant reduction in the strength of composite risers. The reliability analysis is conducted using the Monte Carlo Method, revealing that the composite risers perform well at 4000 m. The degradation in performance from moisture absorption becomes increasingly important at greater depths and needs further investigation for these applications.     

深水管中管钢悬链线立管的非线性动力分析

立管技术是深水资源开发的关键技术之一。管中管钢悬链线立管具有同心的外管与内管，其外管提供机械保护，内管提供油气通道，内、外管之间按照一定的距离安装扶正器以保护绝热材料，在深水油气开发中具有较大的应用价值。充分考虑在位立管承受的复杂载荷条件泡括动边界、波浪与海流载荷、立管自重、海水浮力、管内外静压力），以及整体和局部非线性因素（包括摩擦、滑移、接触、间隙等），采用时域有限元软件ABAQUS实现管中管钢悬链线立管的建模与非线性动力分析。     

水下压缩空气储能系统柔性立管响应特性分析（英文）

With the rapid development of marine renewable energy technologies, the demand to mitigate the fluctuation of variable generators with energy storage technologies continues to increase. Offshore compressed air energy storage(OCAES) is a novel flexible-scale energy storage technology that is suitable for marine renewable energy storage in coastal cities, islands, offshore platforms, and offshore renewable energy farms. For deep-water applications, a marine riser is necessary for connecting floating platforms and subsea systems. Thus, the response characteristics of marine risers are of great importance for the stability and safety of the entire OCAES system. In this study, numerical models of two kinds of flexible risers, namely, catenary riser and lazy wave riser, are established in OrcaFlex software. The static and dynamic characteristics of the catenary and the lazy wave risers are analyzed under different environment conditions and internal pressure levels. A sensitivity analysis of the main parameters affecting the lazy wave riser is also conducted. Results show that the structure of the lazy wave riser is more complex than the catenary riser; nevertheless, the former presents better response performance.     

Participating mass in colliding risers

One of the main challenges in estimating impact energy in collisions between marine risers is the assessment of the riser mass involved in the collision. Evidently the entire riser mass does not contribute to the collision. Hence, the question is: What is the equivalent riser mass which contributes to the impact energy? This article presents three different ways of estimating the riser mass participating in the collision energy. The first method is strictly experimental. The second method uses a numerical experiment together with system identification techniques. The third method is a strictly analytical method, which results in an asymptotically upper bounded estimate of the participating mass. Two risers are examined as case studies. The first riser is a 1 : 100 model scale riser used in collision experiments carried out at Marintek's towing tank in Trondheim, Norway. The second case uses a real world riser in use on the Troll B oil production platform operating in the North Sea. The proposed methods yield consistent and comparable results. Received for publication on Feb. 1, 1999; accepted on July 8, 1999     

Influence of seabed trench formation on fatigue performance of steel catenary risers in touchdown zone

The subsea survey results using remote operating vehicles (ROV) show that trenches with a depth of several riser diameters can be developed underneath the steel catenary risers (SCR). Therefore, an important question in respect of the riser–seabed interaction is, how the trench formation beneath the riser affects the riser fatigue performance in the touchdown zone. A common methodology reported in literature to study the impact of trench formation on riser fatigue life is the insertion of an artificial mathematical expression of the riser profile into the seabed. This study shows that such methodology can be inconsistent and leading to contradictory results. The current paper has employed ABAQUS finite element software and coded a non-linear soil hysteretic model to automatically simulate the variable seabed stiffness and the gradual trench development through the touchdown zone. In this method, the seabed model parameters are initially adjusted to extreme values allowing trench with desired depth to be developed over a moderate number of displacement cycles of the SCR. The design wave scatter diagram is then applied, simulating a generic Spar system, after switching the model parameters to values with normal range. The paper presents the impact of trenches of different depths on the fatigue performance of SCRs in the touchdown zone.