Viscous Hydroelasticity of Riser for Pumping-Up Deep Ocean Water

本研究的目的是发展一种预测深海水抽升的动力分析方法。首先，对振动柔性管道模型进行了运动测量，以研究涡激振动发生的条件。实验结果表明，当Keulegan-Carpenter数大于8时，管发生涡激振动，当管底端运动呈“8”字形时，管的横向运动幅值很大。其次，建立了一个对称涡模型来预测作用在立管元件上的粘性力。该方法适用于Keulegan-Carpenter数小于8的不规则振荡立管单元。为了验证对称涡模型的动力学分析方法，还进行了振动柔性管道模型的运动测量。结果表明，所提出的分析方法可以估计立管在规则和不规则振荡条件下的运动。第三，对内流的影响进行了实验和理论研究。运动测量和考虑内流影响的动力分析结果表明，由于来流反力的作用，有内流时管道的水平位移大于无内流时的水平位移。最后，提出了考虑横向运动的涡激振动动力分析方法。该方法可以模拟8字形运动和具有三个波腹的运动。

The aim of this research is to develop a dynamic analysis method for predicting deep-ocean-water pumping-up risers. Firstly, motion measurements of oscillated flexible pipe models were carried out to investigate conditions when vortex induced vibrations occur. The experimental results suggested that vortex induced vibrations occur at Keulegan-Carpenter number higher than 8, and the transverse motion amplitude becomes very large when the motions of the pipe bottom end form 8-shaped figures. Secondary, a symmetrical vortices model was developed to predict viscous forces acting on riser elements. This method is applicable to irregularly oscillating riser elements at Keulegan-Carpenter number lower than 8. Motion measurements of oscillated flexible pipe models were also carried out to validate a dynamic analysis method using the symmetrical vortices model. The results showed that the developed analysis method can estimate the riser motions in both regularly and irregularly oscillating conditions. Thirdly, effects of internal flow were experimentally and theoretically investigated. The results of motion measurements and the dynamic analyses considering the internal flow effects demonstrated that the horizontal displacement of the pipe with internal flow is larger than that without internal flow due to the reaction force of the intake flow. Finally, a dynamic analysis method considering transverse motions was developed to estimate motions with vortex induced vibrations. This method can simulate 8-shaped motions and motions with three antinodes.