深海系泊平台大幅运动的两次展开分析方法

深海系泊平台在波浪作用下会发生大幅低频漂移和高频振荡的复杂物理现象。因物体运动幅度很大，目前工程中采用的关于平衡位置展开的分析方法已不再合理，理论上也不严格。本研究拟建立一个两次展开的时域分析方法以解决这一复杂的科学问题。具体分析方法是：将系泊平台的复杂运动分解为水平方向的慢漂和六个方向的高频振荡两个部分，采用小波分解和滤波方法实时预报海洋平台的大幅低频慢漂运动轨迹，然后围绕物体的低频慢漂轨迹对流体速度势做泰勒级数展开，在物体低频运动的瞬时物面和平均水面上建立定解问题的边界条件,利用边界元方法进行求解,再与已建立的非线性有限元系泊缆索动力模型相结合建立一个新的波浪与深海系泊平台耦合作用的分析模型。最后，开展实验室实验验证所建数值模型的正确性；开展系统分析，研究各种因素对平台低频运动的影响和规律，明确各种已有分析方法的适用范围和应用条件。

The low frequency drift motion and high frequency oscillation of platforms moored in deep water is a complex physical phenomenon. Due to the large displacement of a platform, all the present analysis methods based on the perturbation with respect to the still position of platform are unreasonable, or not strict. The present study intends to establish a two-steps expansion method in the time domain to solve the complex scientific problem. The strategy of the study is to divide the motion of platform into the large drift motion at low frequency and the oscillation around the drift motion at high frequency, to predict the low frequency drift trajectory of the platform by a wavelet decomposition and filtering method, and then to expand the fluid velocity potential into Taylor series about the body surface at the instantaneous drift position. Boundary conditions will be established at the body surface corresponding to the drift position and the mean water surface, and boundary element method will be used to solve the velocity potential at the body surface, and normal velocity of fluid at the mean water surface. Combining with the previous established mooring line dynamic model by the nonlinear finite element method, a novel coupling analysis model will be established for deep-water moored platform under wave action. Finally, laboratory experiment will be carried out on wave interaction with some moored floating body, and verification of the numerical model will be carried out. At last, benchmark test will be carried out with the new and old numerical models. Through systematic study, applicable ranges and application conditions of various old analysis methods will be given.