Governing Equations and Numerical Solutions of Tension Leg Platform With Finite Amplitude Motion
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摘要: 论证了张力腿平台（TLP）在波浪作用下发生有限振幅运动时，所受惯性力、粘性力、浮力等载荷不仅与波浪场有关，还与瞬时响应有关，是响应的非线性函数；张力腿拉力也是各自由度位移的非线性函数．所以分析TLP受力时必须考虑平台的瞬时加速度、速度和位移，在瞬时位置建立运动方程．据此推导出TLP发生有限振幅运动时的外力计算公式，建立了TLP 6自由度有限振幅运动非线性控制方程．其中考虑了由6自由度有限位移引起的多种非线性因素，如各自由度之间的耦合、瞬时湿表面、瞬时位置等；还包括自由表面效应、粘性力等因素引起的非线性．用数值方法求解所得到的非线性运动方程．对典型平台ISSC TLP进行了数值分析，求得该平台在规则波作用下的6自由度运动响应．用退化到线性范围的解与已有解进行了对比，吻合良好．数值结果表明，综合考虑非线性因素后响应有明显改变．
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关键词:
- 张力腿平台（TLP） /
- 有限位移 /
- 非线性动力响应 /
- 数值解 /
- 波浪载荷
Abstract: It is demonstrated that when tension leg platform (TLP) moves with finite amplitude in waves, the inertia force, the drag force and the buoyancy acting on the platform are nonlinear functions of the response of TLP. The tensions of the tethers are also nonlinear functions of the displacement of TLP. Then the displacement, the velocity and the acceleration of TLP should be taken into account when loads are calculated. In addition, equations of motions should be set up on the instantaneous position. A theoretical model for analyzing the nonlinear behavior of a TLP with finite displacement is developed, in which multifold nonlinearities are taken into account, i. e. finite displacement, coupling of the six degrees of freedom, instantaneous position, instantaneous wet surface, free surface effects and viscous drag force. Based on the theoretical model, the comprehensive nonlinear di-f ferential equations are deduced. Then the nonlinear dynamic analysis of ISSC TLP in regular waves is performed in the time domain. The degenerative linear solution of the proposed nonlinear model is verified with existing published one. Furthermore, numerical results are presented which illustrate that nonlinearities exert a significant influence on the dynamic responses of the TLP. -
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