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深海立管固有振动特性的进一步分析

ISSN号：1007-7294
期刊名称：船舶力学
时间：0
页码：-
分类：O175.1[理学—数学;理学—基础数学] TS734.7[轻工技术与工程—制浆造纸工程]
作者机构：[1]State Key Laboratory of Hydraulic Engineering Simulation and Safety, School of Civil Engineering,Tianjin University, Tianjin 300072, P. R. China
相关基金：The study is supported by the National Natural Science Foundation of China （51239008, 51279130, 51079097） and Science Fund for Creative Research Groups of the Na- tional Natural Science Foundation of China （51021004）.
相关项目：深海立管参激和涡激联合作用振动特性及其疲劳研究

作者：张杰|唐友刚|

关键词：变张力, 参数稳定性, 长度, 深水, FLOQUET理论, 不稳定性, 冒口, 浮动平台, deepwater risers, parametric instability, variable tension, mode coupling

中文摘要：

Parametric instability of a riser is caused by fluctuation of its tension in time due to the heave motion of floating platform. Many studies have tackled the problem of parametric instability of a riser with constant tension. However, tension in the riser actually varies linearly from the top to the bottom due to the effect of gravity. This paper presents the parametric instability analysis of deepwater top-tensioned risers(TTR) considering the linearly varying tension along the length. Firstly, the governing equation of transverse motion of TTR under parametric excitation is established. This equation is reduced to a system of ordinary differential equations by using the Galerkin method. Then the parametric instability of TTR for three calculation models are investigated by applying the Floquet theory. The results show that the natural frequencies of TTR with variable tension are evidently reduced, the parametric instability zones are significantly increased and the maximum allowable amplitude of platform heave is much smaller under the same damping; The nodes and antinodes of mode shape are no longer uniformly distributed along the axial direction and the amplitude also changes with depth, which leads to coupling between the modes. The combination resonance phenomenon occurs as a result of mode coupling, which causes more serious damage.

英文摘要：

Parametric instability of a riser is caused by fluctuation of its tension in time due to the heave motion of floating plat- form. Many studies have tackled the problem of parametric instability of a riser with constant tension. However, tension in the riser actually varies linearly from the top to the bottom due to the effect of gravity. This paper presents the parametric instability analysis of deepwater top-tensioned risers （TTR） considering the linearly varying tension along the length. Firstly, the governing equation of transverse motion of TTR under parametric excitation is established. This equation is reduced to a system of ordinary differential equations by using the Galerkin method. Then the parametric instability of TTR for three calculation models are investigated by ap- plying the Floquet theory. The results show that the natural frequencies of TTR with variable tension are evidently reduced, the pa- rametric instability zones are significantly increased and the maximum allowable amplitude of platform heave is much smaller under the same damping; The nodes and antinodes of mode shape are no longer uniformly distributed along the axial direction and the am- plitude also changes with depth, which leads to coupling between the modes. The combination resonance phenomenon occurs as a result of mode coupling, which causes more serious damage.

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