Effect of Internal Flow on Vortex-Induced Vibration of Submarine Free Spanning Pipelines

At present, most researches on the vortex-induced vibration of submarine free spanning pipelines ignore the effect of internal flowing fluid; furthermore, there are no research reports considering the coupling effect of internal and external fluid with the free span. In this paper, combining Iwan‘s wake oscillator model with the differential equation derived for the dynamic response of submarine free spanning pipelines with inclusion of internal flow, the pipe-fluid coupling equations are developed to investigate the effect of internal flow on the vortex-induced vibration of the free spans. The finite dement approximation is implemented to derive the matrix equations of equilibrium. The Newmark method combined with simple iteration is used to solve the system of equations. The results indicate that the internal fluid flow may cause the shift of resonance band to the lower frequency and a slight decrease in the peak value; the effect will be mare pronounced with the increase of the span length and can be weakened in the presence of the axial tension.     

Analysis of Safe Span Length and Fatigue Life of Submarine Pipelines

Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline.     

海底输液管道内流、轴向力和压强对允许悬空长度的影响

以海底悬跨段输液管道为研究对象,考虑管内流体流动及管道轴向力和压强的作用,对其进行受力分析,导出管道振动微分方程。由于内流流速项的影响,使得导出的管道振动微分方程不能用振型分解法直接求解,故本文将解表示为具有正弦和余弦的对称和反对称的各个空间振型的总和,从而求出悬跨段管道固有频率。为防止管道发生横向涡激振动,用约化速度作为控制条件,求解出管道允许悬空长度。结果表明,管道允许悬空长度随着内流流速、轴向压力和管内压强的增加而减小,随着轴向拉力的加大而增大。     

海底管道疲劳寿命预报方法

海底管道悬跨管段在波流联合作用下非常容易发生疲劳破坏.文中通过多项Galerkin方法对海底管跨的涡激振动方程进行求解,获得管跨系统的时域非线性动力响应,分析疲劳裂纹扩展模型MeEvily模型中各个参数对管道疲劳寿命的影响,在此基础上提出管道疲劳寿命预报方法.     

Experimental Study on Vortex-Induced Vibrations of Submarine Pipeline near Seabed Boundary in Ocean Currents

1 .IntroductionThe submarine pipeline is a commonfacility widely usedfor offshore oil and gastransport . Whena pipeline is installed on a seabed and not buried,unsupportedspans may exist insomelocations ,es-peciallyinthe uneven zones of the seabed.The spa…     

The Effect of Internal Fluid on the Response of Vortex-Induced Vibration of Marine Risers

Based on Iwan‘s wake oseillator model developed with the classical van der Pol equalion, the differential equation for the response of the vortex-induced vihration (VIV) of the riser considering the effect of the internal flowing fluid and the external marine environmental condition is derived. The effect of the intermal flowing fluid on the response of VIV of the riser is studied by means of the Finite Element Method. The results show that the effect of the internal fluid velocity on the VIV of the riser is strong when the natural frequency of the riser is close to the vortex shedding frequency. In addition, the increase of the top tension can decrease the sensitivity of the riser to the internal fluid velocity.     

内流对海底管线涡致振动与疲劳寿命的影响

在复杂的海洋环境条件下，管道的动力学特性受到内外部流体的作用而呈现出新的特点。本文通过对处在海底平稳流动作用下的悬跨管道的涡致振动进行分析，特别地考虑到管道内部流动的作用，给出了内流速度对管道响应幅度的影响，进而指出其对管道疲劳的意义。     

海底管线冲刷悬空及其抑制技术研究综述

海底管线作为海洋工程的重要组成部分,其安全性受到广泛关注。本文简单回顾了国内外学者通过物理实验、理论分析与数值模拟等方法研究海底管线冲刷悬空及防护问题的成果,并对工程中应用较广泛的防护方法的优缺点进行了简单对比,为该领域的进一步研究提供参考。     

Experiments on Interaction Between Current-Induced Vibration and Scour of Submarine Pipelines on Sandy Bottom

In order to understand the dynamic behavior of submarine pipelines exposed to current andthe mechanism of the interaction between current-induced vibration and scour of pipelines on a sandy bot-tom,an experimental investigation is conducted with a small scale model.A test model which can be testedin the flume is set up by taking into account the typical working conditions of the pipelines and by ap-plying the similarity theory.The interactions between the shape of the scour hole and the behavior of thepipeline as well as the flow patterns of the current are detailed,and the interaction mechanism outlined.The effect of vibration of the pipeline on the development of dynamic scour at different stages is foundout.The proposed experimental method and test results provide an effective means for design of marinepipelines against scouring.     

陡波形立管涡激振动疲劳损伤参数敏感性分析

基于柔性杆理论和尾流振子模型计算陡波形立管的涡激振动响应;综合使用S-N曲线法、雨流计数法、Palmgren-Miner线性累积疲劳理论对立管涡激振动导致的疲劳损伤进行计算分析.并以MATLAB为平台编写相应计算程序,将本文计算得到的静力分析结果、固有频率和疲劳损伤分别与专业海工计算软件O rcaFlex和已发表文献进...     

海底管道管跨段在内外流体作用下的竖向动力特性研究

根据在复杂的海洋环境条件下,管道的动力特性受到内外流体的综合作用影响,呈现与陆地管道不同的特点。研究了结构受到外界流体所产生的涡激作用,同时考虑管内恒定流的影响,利用有限元方法对海底管道管跨段竖向振动的微分方程进行求解。在此基础上得出了管跨段在不同外流流速情况下,内流流速与结构动力响应幅值的关系及其对管跨段振动频率的影响,并进一步探讨了管跨失稳时的极限管内流速与跨长的关系,这些结论对于海底管道设计具有一定实际指导意义。     

海底水平管线回流区水流特性研究

针对管线绕流剪切层区的水流特征,利用射流分析的类似方法,通过简化控制方程,从理论上探讨了剪切层区的时均速度分布规律。物理试验中采用ADV测速仪对回流区流场进行了测量,对各流区流速和紊动强度变化趋势进行了讨论,并将试验结果与理论推导进行对比,二者基本吻合,为进一步研究海底管线防护措施提供了理论依据。     

Experimental Study on Coupled Cross-Flow and in-Line Vortex-Induced Vibration of Flexible Risers

In this work, we study the coupled cross-flow and in-line vortex-induced vibration （VIV） of a fixedly mounted flexible pipe, which is free to move in cross-flow （ Y- ） and in-line （ X- ） direction in a fluid flow where the mass and natural frequencies are precisely the same in both X- and Y-direction. The fluid speed varies from low to high with the corresponding vortex shedding frequency varying from below the first natural frequency to above the second natural frequency of the flexible pipe. Particular emphasis was placed on the investigation of the relationship between in-line and cross-flow vibration. The experimental results analyzed by using these measurements exhibits several valuable features.     

Dynamic Analysis of Submarine Pipelines on an Elastic / Viscoelastic Foundation

This paper presents a new finite element method for solving static and dynamic problems in laying operation of pipelines. The effect of the viscoelastic soil behavior is considered by using the Pasternak foundation model. Some examples are also presented.     

Study on Model Tests and Hydrodynamic Force Models for Free Spanning Submarine Pipelines Subjected to Earthquakes

A test rig is built to model the dynamic response of submarine pipelines with an underwater shaking table in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China. Model tests are carried out to consider the effects of exciting wave directions and types. Based on the experimental results, two hydrodynamic force models derived from Morison equation and Wake model are presented respectively. By use of hydrodynamic force models suitable for free spanning submarine pipelines under earthquakes, discretized equations of motion are obtained and finite element models are established to analyze dynamic response of free spanning submarine pipeline subjected to multi-support seismic excitations. The comparison of numerical results with experimental results shows that the improved Morison and Wake hydrodynamic force models could satisfactorily predict dynamic response on the free spanning submarine pipelines subjected to earthquakes.     

Research on Fatigue invalidation of A Submarine Pipeline Span Subjected to Waves and Currents

1 .IntroductionRecently, more and more importance is attached to the development of offshore oil and gas alloverthe world and many submarine pipelines have been laid.Submarine pipelines are the lifeline ofthe transportation of offshore oil and gas .Submar…     

圆柱涡激振动研究进展与展望

圆柱涡激振动广泛存在于机械工程、海洋工程等诸多领域,研究者们取得了许多研究成果,而系统综述圆柱涡激振动的论文距今已近10 a,因此,有必要对近10 a的研究进展进行系统分析。文中系统地总结了近10 a圆柱涡激振动研究成果,阐述了圆柱涡激振动的尾流模态和其对应的响应分支之间的因果关系,分析了影响圆柱涡激振动的关键因素(如质量比、阻尼比和雷诺数)对涡激振动响应的影响,介绍了圆柱涡激振动最大响应振幅的曲线拟合公式及其局限性,最后对圆柱涡激振动的研究方向提出建议。     

Experimental Study of Hydrodynamic Loading on Submarine Composite Pipelines under the Action of Waves and Current

- This article is aimed at the experimental study of the hydrodynamic loading induced by waves and current acting on the JZ 20-2 submarine composite pipelines. The corresponding hydrodynamic coefficients obtained in this experimental study can be applied to engineering projects.     

国外对海底电缆管道违法行为处罚对我国的启示 ——以新西兰和澳大利亚为例

近年来,随着海洋油气资源的大规模开发以及跨海电力和通信需求的增加,我国海底电缆管道建设得到迅速发展,近海海底电缆管道分布愈来愈密集,同时与之相关的违法行为也日益增多。目前,我国尚未出台海底电缆管道保护法,现有的处罚规定较为分散、模糊,且处罚力度小,甚至处罚规定之间存在混乱和矛盾的问题,导致难以对海底电缆管道违法行为实施有效打击。澳大利亚和新西兰作为海洋管理经验相对成熟的国家,对海底电缆管道的法律保护较为成熟,其中对海底电缆管道违法行为的处罚分类和方式等,有诸多值得我国学习之处。基于此,文章从违法行为处罚角度深入分析我国海底电缆管道管理与保护的相关制度现状,介绍新西兰和澳大利亚海底电缆管道法律制度概况及处罚规定的特点并与我国进行比较,为完善我国海底电缆管道违法行为的处罚规定和今后的海底电缆管道立法提出了在《中华人民共和国刑法》中增设破坏海底电缆管道罪;制定《海底电缆管道法》等建议。     

冷却剂参数对铣槽喷管低周疲劳寿命的影响

采用有限体积流固耦合计算方法、非线性有限元热结构耦合分析方法和局部应变法研究大面积比铣槽喷管三维再生冷却槽道在循环工作条件下的热结构变形与低周疲劳寿命,并对比分析了冷却剂质量流量与入口温度对铣槽喷管疲劳使用寿命的影响。计算结果表明,铣槽喷管热结构响应呈现复杂的三维效应,应变较大位置主要分布在与肋连接的内衬区域,喷管中部的残余应变量最大;冷却槽道低周疲劳寿命分布和热结构响应基本一致,最小寿命位于喷管中部与肋相连的内衬区域燃气侧;随冷却剂质量流量增加,铣槽喷管低周疲劳寿命不断提高;随冷却剂入口温度增加喷管尾部低周疲劳寿命值不断降低,而喷管中前部的低周疲劳寿命值却不断提高,当冷却剂入口温度为280K左右时,本文的铣槽喷管总体使用寿命达到最大。 