The nonlinear bifurcation and chaos of coupled heave and pitch motions of a truss spar platform
The nonlinear bifurcation and chaos of coupled heave and pitch motions of a truss spar platform
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DOI：
10.1007/s11802-015-2592-2
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发表时间：
2015-08
影响因子：
1.6
通讯作者：
Lei Huang;Li-qin Liu;Chunyuan Liu;You-gang Tang
中科院分区：
文献类型：
--
作者：
Lei Huang;Li-qin Liu;Chunyuan Liu;You-gang Tang
本文对桁架式Spar平台的非线性动力学行为进行了数值研究。考虑到垂荡模态和纵摇模态之间的相互影响，建立了规则波作用下Spar平台船体的垂荡与纵摇耦合运动方程。为了分析平台的非线性运动，构造了三维最大李雅普诺夫指数图和分叉图，计算了平台响应的Poincaré映射和功率谱。研究发现，平台运动对波浪频率敏感。随着波浪频率的变化，平台会发生复杂的非线性运动，包括1/2亚谐运动、准周期运动和混沌运动。当波浪频率接近平台垂荡模态的固有频率时，平台以准周期运动和混沌运动交替进行。对于一定范围的波频率，平台以完全混沌的运动移动。导致平台混沌运动的波浪频率范围随波高的增加而增加。三维最大李雅普诺夫指数图和分叉图揭示了Spar平台在不同波浪条件下的非线性运动。
This paper presents the results from a numerical study on the nonlinear dynamic behaviors including bifurcation and chaos of a truss spar platform. In view of the mutual influences between the heave and the pitch modes, the coupled heave and pitch motion equations of the spar platform hull were established in the regular waves. In order to analyze the nonlinear motions of the platform, three-dimensional maximum Lyapunov exponent graphs and the bifurcation graphs were constructed, the Poincaré maps and the power spectrums of the platform response were calculated. It was found that the platform motions are sensitive to wave frequency. With changing wave frequency, the platform undergoes complicated nonlinear motions, including 1/2 sub-harmonic motion, quasi-periodic motion and chaotic motion. When the wave frequency approaches the natural frequency of the heave mode of the platform, the platform moves with quasi-periodic motion and chaotic motional ternately. For a certain range of wave frequencies, the platform moves with totally chaotic motion. The range of wave frequencies which leads to chaotic motion of the platform increases with increasing wave height. The three-dimensional maximum Lyapunov exponent graphs and the bifurcation graphs reveal the nonlinear motions of the spar platform under different wave conditions.