FPSO串靠外输系统动力分析

Dynamic analysis of FPSO tandem offloading system

FPSO串靠外输方式因其对环境的适应性好,安全性较高,是FPSO原油外输的主要方式。该文考虑了风、流和系泊缆索的耦合动力,建立了FPSO串靠多浮体系泊系统的时域耦合运动模型,其中浮体时域水动力系数由频域的结果通过快速傅立叶变换转换得到。数值求解时,浮体时域运动方程采用Newmark-β法,系泊缆索采用时域非线性有限元方法。基于自主开发的Fortran计算程序对南海海域一艘张紧式系泊FPSO与其配套的躺底式系泊穿梭油轮及两船间系泊大缆组成的串靠输油系统进行了理论计算,得到了FPSO及穿梭油轮的纵荡运动响应,系泊缆索上端点张力,系泊大缆张力等时间历程。通过谱分析讨论了低频波浪力和波频波浪力对FPSO串靠系泊系统的作用。同时探究了风向和流向对FPSO串靠系统的影响。该串靠多浮体系泊系统耦合动力模型能合理解释物理现象,可用于分析实际作业的串靠外输系泊系统。

FPSO tandem offloading system is the main way of FPSO crude oil transmission because of its good adaptability to the environment and better security. In this paper, the coupled forces of wind, current and mooring cables are considered. Coupled motion model of FPSO tandem offloading multi-body mooting system in time domain is established. The floating bodies＇ hydrodynamic coefficients in time domain are transferred from frequency domain by using the method of FFT. The motion equations of floating bodies in time domain are solved by Newmark- fl method, and mooring cables are simulated by nonlinear finite element method. Using the Fortran language, the theoretical calculation is carried out for a FPSO tandem otTloading system consisting of a taut mooring FPSO, a matched catenary mooting shuttle tanker and the mooring line between two ships. And the two floating bodies＇ motion response time history curves, mooring cables＇ top point tension time history curves and mooring line＇s tension time history curves are obtained. Also, by means of spectrum analysis, the influence of low frequency wave forces and high frequency wave forces for the whole system is analyzed. This coupled dynamic model of multi floating tandem mooring system can reasonably explain the physical phenomena, and it can be used to analyze FPSO tandem offloading mooring system working in actual sea conditions.