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抽水立管的动态分析方法。首先，对振动软管模型进行了运动测量，研究了涡激振动发生的条件。实验结果表明，涡激振动发生在Keulegan-Carpenter数大于8时，当管子底部运动形成8字形时，横向运动幅度变得很大。其次，建立了一个对称的涡流模型来预测作用在提升管上的粘性力。该方法适用于Keulegan-Carpenter数小于8的非规则振动立管元件。为了验证对称旋涡模型的动力学分析方法，还进行了振动柔性管模型的运动测量。结果表明，所提出的分析方法可以很好地估计规则和非规则振动条件下的立管运动。第三，对内部流动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学分析结果表明，由于进气反力的作用，有内流管道的水平位移大于无内流管道的水平位移。最后，提出了一种考虑横向运动的动力分析方法来估计涡激振动的运动。这种方法可以模拟8字形的运动和有三个安定标的运动。

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.