A Study on Dynamics of Flexible Marine Riser

在这项研究中，一个数值方法来分析的运动，剪切力和力矩的立管。首先利用“汉密尔顿原理”导出立管动力学的全非线性运动方程，然后在适当的假设下将其线性化，以便于数值计算。本文提出了一种基于Galerkin法和Newmark-b法的立管动力学数值模拟方法。为了验证所提出的模拟方案的准确性，在实验水池中进行了各种实验条件下的模型实验，这些实验中使用了高柔性立管模型。立管模型的顶端在无波无流的情况下作简谐振动。沿立管轴线Z在五至六个垂直位置沿着布置十至十二个CCD摄像机，并且在每个垂直位置处沿X-Y方向固定两个摄像机，使得可以测量立管的三维运动。一个摄像头可以跟踪三个镜头 ...更多信息 同时测量两个点，可以检测出立管模型在每个测量点处的斜率。在每个实验中，在立管模型的顶端安装一个五分量测力传感器，以测量施加在模型上的力和力矩。建立了一套全面、准确的模型试验系统，并对模型试验结果进行了多方面的分析和讨论。通过与数值模拟结果的比较，证实了所提出的数值模拟方法能够准确地描述立管的纵向运动、力和力矩，但在极强的运动范围内除外。在高振荡频率和大振荡幅度的范围内，实验和模拟之间的差异变得明显的数字，这可能是由于线性化的运动方程与小张力变化的假设或涡激振动的影响。最后一年，发展了“振荡流中海洋立管涡激振动”的数值模拟方法，并通过与实验的对比验证了该方法的准确性。少

In this study, a numerical method is developed for analyzing the motion, shear force and moment of a riser. Firstly full nonlinear equations of motions for the riser dynamics are derived using 'Hamilton's principle' and then linearized under appropriate assumptions for convenience of the numerical work. A numerical simulation scheme for riser dynamics developed in this paper is based on the 'Galerkin method' and 'Newmark-b method'. For validating accuracy of the eveloped simulation scheme, model experiments are carried out in an experimental tank under various experimental conditions, Highly flexible riser models are used in these experiments. The top end of the riser model is forced to oscillate harmonically without wave or current. Ten to twelve CCD cameras are arranged at five to six vertical positions along the riser axis Z and at each vertical position two cameras are fixed in X-Y directions so that the three-dimensional riser motion can be measured. One camera can track three clo … More se points simultaneously and the slope of the riser model at each measured point can be detected. In each experiment, a five-component load cell is installed at the top end of the riser model to measure the force and moment exerted on the model. A comprehensive and accurate experimental system has been established.Results of model experiments are analyzed and discussed in various aspects. By comparing the results of the inline motion in the same direction as the forced oscillation with those of numerical simulations, it is confirmed that the developed numerical simulation scheme can describe accurately the riser inline motion, force and moment except in the range of extremely strong motion. In the range of high oscillation frequency and large oscillation amplitude, the discrepancy between experiments and simulations become visible in figures, which may be attributed to the linearization of the motion equations with the assumption of small tension variation or to the effects of vortex-induced vibration. They fall on the future work to be researched further.In the final year, the simulation method of "Vortex Induced Vibration of Marine Riser in Oscillating Flow" has been developed and its accuracy was confirmed by comparing with experiments. Less