Governing equations and numerical solutions of tension leg platform with finite amplitude motion

• Published in: Applied mathematics and mechanics 2007, Vol.28 (1), p.37-49
• Main Author: 曾晓辉 沈晓鹏 吴应湘
• Format: Article
• Language: English
• Subjects: Amplitudes; Differential equations; Displacement; Mathematical analysis; Mathematical models; Nonlinear dynamics; Nonlinearity; Platforms; 张力腿海洋钻井平台; 数值解; 有限位移; 波浪荷载; 非线性动态响应
• ISSN: 0253-4827; 1573-2754
• DOI: 10.1007/s10483-007-0105-1

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 theo- retical 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 displace- ment, 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 differential 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.