深水卸载浮标系统具有相对较小的排水量和惯性,其系泊缆索的质量、阻尼和刚度会对卸载浮标系统产生非常大的影响,因而对浮标和其系泊系统进行准确的耦合动力响应分析十分重要。应用边界元方法计算浮标的水动力,通过快速傅立叶变换,将频域计算结果变换到时域;基于全量的拉格朗日表述和两节点的等参索单元,应用几何非线性有限元方法和Newmark方法计算了系泊缆索张力;最后应用四阶龙哥库塔法计算浮标及其系泊缆索的时域耦合运动方程,得到浮标运动响应和缆索张力。
The deepwater offloading buoy system has relatively small displacement and inertia,so that the mass,damping,and stiffness of the mooring lines have a great impact on the buoy's dynamic response,thus the accurate coupled analysis of the dynamic response on buoy and its mooring system is particularly important.Applying the boundary element method to calculate hydrodynamic forces of buoy,results in frequency domain can be transformed into the time domain by fast Fourier transform.Based on the total Lagrange formulation and the two-node isoparametric cable element,this paper applies the geometric nonlinear finite element method and Newmark method to calculate tensions in mooring lines.Forth order Runge-Kutta integration scheme is applied to calculate coupled motion equations of buoy and mooring lines in time domain,then the motion response of buoy and tensions in mooring lines can be obtained.