严重段塞流引起的海洋立管振动响应

DYNAMIC RESPONSE OF A MARINE RISER CAUSED BY SEVERE SLUGGING FLOW

基于改进的严重段塞流瞬态数学模型和平面刚架理论,建立严重段塞流海洋立管耦合振动数学模型,对数学模型进行求解,研究了严重段塞流引起的海洋立管振动响应。数值模拟过程中,采用欧拉法计算严重段塞流流动参数,利用Galerkin法对立管结构动力学方程进行有限元离散,Newmark-β法求解离散方程。为了提高计算效率和精度,采用了变时间步长逐步积分方案。将数值模拟结果与实验数据进行对比,验证了数学模型和数值方法的准确性。对严重段塞流引起的立管系统位移响应、内力和支承力变化进行了深入分析。结果表明:立管系统的振动响应、内力变化规律与严重段塞流的周期性特征密切相关;弹性基础可以极大降低管道结构的振动幅度及内力,尤其是下倾管的弯曲内力;上升管的高频振动幅度较大,轴力和弯曲内力变化也较大。严重段塞流引起海洋立管振动响应的分析对海洋立管设计及其支承防护具有重要的指导意义。

A fluid-structure interaction model for a marine riser system on elastic foundation conveying severe slugging flow was developed based on the modified severe slugging transient model and theories of plane frame structure, and solved to simulate the dynamic response of a marine riser system caused by severe slugging flow using numerical methods. The Eulerian method was used to solve the equations of severe slugging flow. Galerkin＇s method was adopted to discretize the dynamic equations in space and Newmark-~ method was employed for time-domain integration of the discretized equations. Variable time-steps were employed for higher computational efficiency and accuracy in the integration process. The comparisons of simulation results with the experimental data show that the mathematical model and numerical methods are reasonable. Detailed analysis of dynamic response, internal force, and reaction force of the hybrid riser reveals that the dynamic response of hybrid riser is closely related to the periodic characteristics of severe slugging flow, and the elastic foundation can suppress the vibration amplitude and the internal force, especially bending stress of the downward pipeline,significantly. The amplitude of high frequency vibration is large and the axial stress and bending stress oscillate acutely. These analyses are significant to guide the design of marine risers.