细长海洋立管涡激振动预报模型

涡激振动预报对于深水环境中的细长海洋结构物的设计至关重要.近年来出现的若干经验模型基于圆柱体受追振荡实验数据.文中介绍了细长海洋结构物涡激振动预报工具的发展,进而提出了一种基于圆柱体受迫振荡实验数据的预报模型.与现有的类似模型相比较,该模型更加直接地利用了原始模型实验数据,并且将立管的有限元模态分析并入到响应预报当中,以计及立管物理参数的不均匀特性.利用近期立管模型在阶梯状分布流以及剪切流中的涡激振动响应实验测量数据,验证了该模型的有效性.该模型的计算结果表明,立管的模态振型、模态频率与涡激振动响应高度耦合,并且对于低质量比的情况尤为明显.文中还指出了类似的基于受迫振荡圆柱体实验数据的预报模型存在的缺陷.

A Prediction Model for Vortex-Induced Vibration of Slender Marine Risers

The prediction of vortex-induced vibration is very important for design of slender marine structures in deep water. Based on the data from forced oscillation tests of rigid cylindrical sections,many empirical tools were developed.This paper introduces the evolution of analytic tools for ⅤⅣ response of slender marine structures,and then put forward a prediction model for ⅤⅣ of a slender riser in which fluid force coefficients obtained in forced oscillation tests are applied more directly than other similar models. Finite element method is integrated into this model to account for the varying tension,flexural rigidity and mass density along the riser. The capability of the proposed model is validated by model tests of risers in stepped and in sheared currents. It shows that the modal shape and mode frequency are highly coupled with the ⅤⅣ response of a marine riser with low mass ratio.The limitations of such methods based on forced oscillation tests are also pointed out.