波流载荷作用下的下入安装立管横向动态特性

Lateral Dynamic Characteristics of Riser Under Wave-Current Load During Running and Installation

为了研究海洋立管在下入水下设备安装过程的横向动态位移及其下部弯矩变化规律,建立了海洋下入立管的横向动态承载方程、波流载荷计算方程。结合网格离散、边界条件及计算求解稳定性的分析,应用Matlab求解了波浪速度、管柱壁厚和水深变化下的立管横向变形、最大位移和位置,以及位移及弯矩动态波动过程。研究结果表明:距离立管底部50 m内的横向位移、弯矩随时间周期性波动逐步增大,立管最大横向位移与波浪速度近乎呈正比,且弯矩波动幅度及最大弯矩均随海流速度的增大而增大;随着壁厚的增大,立管抗弯强度的增大使得立管的最大位移减小、底部的弯矩幅度减小;在相同张紧力系数下,随着水深的增大,最大横向位移增大、底部的弯矩波动周期减小、弯矩波动变化值减小,最大位移位置自水深“1/3”向海面靠近。研究结果可为海洋立管下入安装设备时的安全作业控制提供基础,并为下入设备分析的上部边界提供条件。

In order to study the lateral dynamic displacement and lower bending moment variation of the marine riser during running and installation,the lateral dynamic load equation and wave-current load equation were established.Based on the analysis of grid discretization,boundary conditions and computation robustness,the equations were solved using Matlab to determine the lateral deformation,lateral maximum displacement and position of the riser with the changes in the wave velocity,pipe wall thickness and water depth,as well as the dynamic fluctuation processes of the displacement and bending moment.The results show that the lateral displacement and bending moment 50 m above the riser bottom fluctuate periodically and grow gradually with time.The lateral maximum displacement of the riser is almost proportional to the wave velocity,and the bending moment fluctuation amplitude and maximum bending moment increase with the increasing wave velocity.With the increase in the wall thickness,both the maximum displacement of the riser and the bending moment amplitude at the bottom decline,due to the increased bending strength of the riser.Given the same tension coefficient,the lateral maximum displacement increases,the cycle of bending moment fluctuation at the bottom reduces,and the magnitude of bending moment fluctuation declines,with the increasing water depth,and the maximum displacement position shifts toward the sea surface from 1/3 of the water depth.The research findings provide the basis for work safety control during the running and installation of marine riser and also upper boundary conditions for the analysis of underwater equipment.