气液严重段塞流混输管线与立管系统涡激振动机理及其理论模型研究

The inclined pipeline-riser system is needed to transport oil with water and associated gas from submarine wellheads up to offshore platform systems during exploitation of deep-water offshore oil and gas.Severe slugging is a specially harmful flow phenomenon which typically occurs in the pipeline-riser system.Such a system will not only experience fatigue damage of riser due to vortex induced vibration generated by ocean current,but also vibration damage of the whole system due to pressure oscillation generated by the severe slugging.Moreover,such a severe slugging will also cause strongly nonlinear and unsteady VIV phenomena of deep-water risers in the cross-flow,in-line and axial directions due to the fact that the mass distributions of the gas-liquid mixture slug in the riser are unsteady state.However,the VIV mechanism and its theoretical model for such a deep-water pipeline-riser system with the gas-liquid severe slugging have attracted less attention. Based on such a current state of the art,a theoretical modelfor predicting strongly nonlinear VIV responses in the cross-flow,in-line and axial directions of the deep-water riser under the action of the severe slugging will be established.The model test method based on the towing-tank will be developed.The strongly nonlinear and unsteady VIV mechanism for the deep-water riser under the coupled interaction between the severe slugging and ocean current will be clarified and then the corresponding VIV characteristics will be obtained.In the present project both the theoretical ground and technology foundation are provided for the design and application of the pipeline-riser system with the gas-liquid mixture transport during the exploitation engineering of deep-water offshore oil and gas.

在深海油气开采系统中，将原油及其伴生气从海底井口输送到海面平台预处理系统时，需要经过一段沿海底铺设的下倾管道和立管系统,严重段塞流是该类管型中常见的一种特殊有害流动现象。对这种管线与立管系统，除了会遭受海流导致的立管涡激疲劳损伤外，还会遭受严重段塞流压力脉动导致的整个系统的振动破坏。另外，由于立管中气液混合液塞的质量分布是非稳态变化的，因此严重段塞流现象还会导致深海立管横向、顺流向及轴向强非线性耦合的非稳态涡激振动现象。然而，有关严重段塞流对深海立管系统涡激振动的影响机理及其理论模型等问题，尚需开展探索性研究。有鉴于此，本课题将建立严重段塞流作用下深海立管横向、顺流向及轴向强非线性耦合的涡激振动理论模型，发展基于船模拖曳水池的模型实验方法，阐明严重段塞流与海流耦合作用下深海立管的强非线性和非稳态涡激振动响应机理及其规律，为气液混输管线与立管系统在深海油气工程中的应用提供理论依据及技术支撑。

在深海油气开采系统中，将原油及其伴生气从海底井口输送到海面平台预处理系统时，需要经过一段沿海底铺设的下倾管道和立管系统, 严重段塞流是该类管型中常见的一种特殊有害流动现象。对这种管线与立管系统，除了会遭受海流导致的立管涡激疲劳损伤外，还会遭受严重段塞流压力脉动导致的整个系统的振动破坏。另外，由于立管中气液混合液塞的质量分布是非稳态变化的，因此严重段塞流现象还会导致深海立管横向、顺流向及轴向强非线性耦合的非稳态涡激振动现象。然而，有关严重段塞流对深海立管系统涡激振动的影响机理及其理论模型等问题，尚需开展探索性研究。有鉴于此，本课题针对相关问题，开展了深入系统的研究。.对卧底管系统采用分层流理论模型，立管系统采用分相流理论模型，建立了卧底管-立管系统气液严重段塞流的一维瞬态理论模型。对下倾管-垂直立管/悬链线立管两类系统，将数值模拟结果与文献中的实验结果进行对比，研究表明该理论模型对严重段塞流周期和压力波动幅值的数值模拟结果与实验结果吻合良好，而且能够成功地模拟实验中发现的四类流型。在此基础上，利用理论模型进一步对严重段塞流压力波动与周期，立管内气液流体速度、含气率及质量分布特性等进行了数值模拟分析，获得了这些流动参数的变化规律。.针对管线与垂直立管系统内严重段塞流的流动特性，建立了一种高效的不完全依赖于实验参数的一维瞬态理论预测模型。该模型不仅能够预测不同类型严重段塞流的发生范围，还能得到压力、周期、流量、气液速度、含气率和折算速度等严重段塞流特性参数，并可对管道系统内气液流态的变化进行实时判别。.为进一步考虑减小涡激振动的问题，采用脱体涡模拟结合湍流分离的方法对弱电解质中电磁力作用下湍流边界层分离圆柱绕流场及其升(阻)力特性进行了数值模拟和分析。结果表明，电磁力延缓圆柱体湍流边界层的流动分离，减弱圆柱体湍流绕流场中在流向和展向上大尺度漩涡的强度，有助于减小涡激振动的产生。