张紧式系泊桁架式Spar平台纵荡-横荡-垂荡固有运动特性研究

Study on natural motion performances in surge,sway and heave direction of a Truss-Spar platform with taut mooring system

针对深海桁架式Spar平台,考虑三点张紧式系泊定位,研究其纵荡、横荡和垂荡三个自由度的固有运动特性.考虑纤维缆索的材料非线性与几何非线性特性,对缆索力学平衡方程重新推导计算系泊缆索张力与位移的变化关系.采用准静态方法,建立考虑系泊作用的平台耦合系统纵荡、横荡和垂荡运动方程,数值求解平台固有运动特性,并讨论系泊条件对平台自振特性的影响.结果表明,在平台小幅运动下,系泊回复力与位移基本呈线性关系,但随着平台位移的增大,系泊回复力随位移变化开始表现出一定的非线性;系泊条件的改变将会改变平台水平运动的固有频率;系泊系统对垂荡运动的固有特性影响不大.

Natural characteristics in surge,sway and heave direction of a Truss Spar platform located in three points with taut mooring lines were investigated in this paper. An empirical equation of non-linear material as well as non-linear material was carried out to simulate the static force of polyester rope which varies due to the strain of the rope,and the equivalent restoration force of mooring system changing with offsets can be calculated with newly derived equations of equilibrium. Considering coupling between a spar and its mooring lines by using quasi static analysis,the coupled equations for surge,sway and heave motions were established. Natural properties can be figured by mathematical methods,and the effects of mooring system on spar can be seen. It shows that the restoration force of mooring lines is linear when small motions appear,but seems to become non-linear with larger displacement. There are differences between the natural frequencies of a spar when under different mooring conditions in surge and sway directions,Else,mooring lines add with little effect on the natural performance of heave.