海洋平台垂荡作用下立管的非线性涡激振动特性研究

Nonlinear vortex-induced vibration characteristics of riser under heaving motion of offshore platform

立管是海洋工程中常用的一种典型细长体结构物,研究立管在海洋平台垂荡和内外流体共同作用下的非线性动力学特性具有重要的学术意义和应用价值。本文采用Hamilton原理和Galerkin方法建立了顶张力立管的二维非线性动力学模型,将平台垂荡运动模拟为随时间变化的顶端张力,研究海洋平台运动和立管非线性涡激振动的耦合位移响应。研究结果显示,增加顶张力可以改变结构的固有频率,在可变张力作用下,立管的位移响应在相邻模态之间可以相互转换。通过与已有实验数据进行对比,验证了本文分析方法和数值计算结果的合理性。本文研究结果可为海洋立管的非线性涡激振动分析提供理论参考。

Risers are a typical kind of slender structures commonly used in marine engineering. It is of great academic significance and application value to study the nonlinear dynamic characteristics of the riser under the combined action of the heaving motion of a offshore platform and the fluid inside and outside of the riser.By simulating the heaving motion of the platform as a time-varying top tension, Hamilton’s principle and the Galerkin method were used to establish the two-dimensional nonlinear dynamic models of the riser with top tension, and the coupled-displacement responses of the motion of the offshore platform and the nonlinear vortex-induced vibration of the riser were studied. It is shown from the investigations that increasing the top tension can change the natural frequencies of the structure. Under the action of variable top tension, the displacement responses of the riser can be converted between the adjacent modes.The rationality of the present analytical method and numerical results was validated by comparing with the existing experimental data. The research results in this paper provide a theoretical reference for nonlinear vortex-induced vibration analysis of marine risers.