摘要
随着深海油气资源的开采,越来越多的研究者开始关注海洋立管的涡激振动问题。在海洋环境下,洋流是海洋立管的涡激振动的主要原因。当洋流流经立管时会在立管的两侧产生交替的泄涡,导致立管受到横流向和顺流向的脉动流体力。这被认为是海洋立管涡激振动的主要诱因。海洋立管的涡激振动是一个异常复杂的工程问题,它涉及许多科学上悬而未决的难题,如紊流、流动分离、分离点的漂移等等。此外,事先无法确定的立管的位置和立管与洋流之间的相互作用又大大增加了解决这一问题的难度。尽管近几十年里科学界在此方面做了大量的研究工作,一个能够准确、高效、经济地预报海洋立管涡激振动的方法仍然没有得到。即便如此,最近的研究工作依然在许多方面作出了突出的成就。首先介绍了涡激振动的背景知识和基础理论。随后,回顾了近年来海洋立管涡激振动方面的研究成果。接着,重点介绍了当前海洋立管涡激振动领域内的两个热点研究问题,即:在多大程度上立管的顺流向振动能够影响立管的横流向振动,以及尾流的三维效应是如何影响立管的涡激振动响应的。最近的研究发现,当结构与流体的质量比小于6时,顺流向振动能显著增大横流向振动的振幅。最近的研究还发现,立管尾流的三维特性和立管受到流体力的轴向相关度有密切关系。随着流动的发展(海流折合速度从0增加到12),立管尾流的三维特性发生变化,在初期,立管尾流的三维特性不明显,流体力的轴向相关度基本等于1,也就是说,流体力和立管的位移响应是同步的,因此能量不断地由海流向立管转移,导致立管的振幅不断增大。当海流折合速度大于6时,流体力的轴向相关度由1锐减到负值,此时,立管尾流的三维效应显著。最后针对今后海洋立管的涡激振动的研究提出一些建议。
With the increasing production of deep-sea oil and gas,more and more efforts have been put into the research of vortex-induced vibration（VIV） of marine riser.In the ocean environment,the VIV of marine riser is mainly caused by the sea current.When current passes by the marine riser,alternative vortex-shedding occurs at each side of the riser,which results in cross-flow and fair-flow pulsating forces acting on the riser.This is considered to be the source of the VIV of marine riser.The VIV of marine riser is such an intricate engineering problem that it involves many unresolved difficult problems,such as turbulent flow,flow separation,separation point shifting,etc.Moreover,the undetermined position of marine riser and the interaction between the flow and marine riser significantly increase the complexity of resolving the problem.Despite several decades of intensive research work,an effective method that can accurately,efficiently and economically predict the VIV responses of marine riser in the sea current has still not yet emerged.However,recently research work still made a lot of contributions to this difficult problem.Many theoretical,empirical,experimental and numerical methods have been presented in journals and international conferences.In this paper,the background knowledge and basic theory of VIV is firstly presented and then,the achievements made in the study of VIV of the marine riser in recent years are reviewed.After that,two hot-spot issues on VIV of marine riser,i.e.,to what extent can the fair-flow vibration impact the cross-flow vibration and how does the three-dimensionality of the wake affect the VIV of marine riser.Conventionally,it is believed that the fair-flow vibration of marine riser has smaller amplitude by an order of magnitude than the cross-flow vibration,and thus has little effect on the cross-flow vibration.However,recent research work found that fair-flow vibration may increase the amplitude of the cross-flow vibration significantly when the structure-fluid mass ratio is smaller than 6.On the other hand,the vortex structure in wake flow was always simplified as a two-dimensional flow in previous studies of VIV.But actually,any vortex structure is three-dimensional.Recent research shows that the three-dimensional feature of the wake flow has a close relationship with the axial correlation of fluid force on the riser.With the development of the current（the nominal reduced velocity of current increasing from zero to 12）,the three-dimensional feature of the wake flow varies.On the early stage it is not obvious and the correlation coefficient of fluid force is almost equal to 1.That is to say,the fluid force and the marine riser＇s displacement are synchronous and energy is transported from the current to the riser continuously,which leads to increasing vibration amplitude of the riser.When the nominal reduced velocity exceeds 6,axial correlation coefficient of the fluid force decreases abruptly from 1 to a negative value.At that time,the three-dimensional effect of the wake flow is significant.The fluid force turns from providing energy to the marine riser to consuming energy of the marine riser,from driving riser＇s vibration to limiting riser＇s vibration.This can be considered as cause of the ＂self-limited＂ characteristics of the VIV response of marine riser.At the end of the paper,some conclusions and recommendations for future research work are made.
出处
《海洋学研究》
2009年第4期95-101,共7页
Journal of Marine Sciences
关键词
涡激振动
海洋立管
综述
vortex-induced vibration marine riser overview
