系泊系统的时域仿真及其非线性动力学特性分析

应用时域仿真的方法研究了系泊系统的非线性动力学特性。以三阶操纵运动方程为基础,引入定常的风力、潮流作用力和二阶波浪力,建立了系泊系统三自由度的运动微分方程。在此数学模型的基础上,建立了系泊系统的多自由度的计算机仿真模型。在风浪流联合作用的情形下,对一艘单点系泊油轮的动力学行为进行了仿真研究。以潮流速度和系缆程度为分岔控制参数,在参数平面上给出了局部分岔集。研究表明,系泊系统的动力学行为具有强烈的非线性特征。在仿真过程中观察到了吸引子的共存和Hopf分岔。局部分岔集将参数平面分为3个系统动力学行为本质不同的区域。极值系泊力水平与系泊系统的动力学行为有着密切的关系。对于单点系泊船舶而言,顶风顶浪顶流的状态并不一定是最为危险的工况。局部分岔集的确定为系泊系统参数的选择提供了决策依据。

Time domain simulation research on the dynamic responses and dynamic characteristics of mooring systems

Introducing uniform tidal current forces, wind forces and steady second order wave forces, motion mathematic model of three degree-of-freedom (3-DOF) of mooring systems was established based on a nonlinear three order vessel maneuvering mathematical model,which included the surge, sway and yaw motions of the moored vessels.Based on this mathematic model, the computer simulation model of 3-DOF motions of mooring systems was built up.Time domain simulations were carried out with a single point mooring tanker exposed to wind, waves, and current. Hopf bifurcation, coexistence and jumping of different attractors were observed.Local bifurcation set and stability charts were obtained in the bifurcation parameters space, while current velocities and mooring line lengths were defined as bifurcation controlling parameters. The results show that there are strong nonlinear characteristics in motion responses of moored ships.It is also shown that perhaps the case is not the most dangerous for single point mooring vessels,in which the moored vessels were exposed to head wind, waves and current. According to these results, the dynamical characteristics of a mooring system could be clarified clearly, which could provide a kind of scientific basis for the choice of the system parameters in the design stage of mooring systems.