The Slow-drift Oscillation of Floating Structure

在张力腿平台等半潜式海洋浮式结构物系泊系统设计中，慢漂振荡是一个重要问题。本课题通过TLP模型和TLP截面模型对作用在TLP上的粘性阻尼力进行了基础研究。通过比较链条系泊的浮式结构和螺旋弹簧系泊的浮式结构在不规则波浪中的浪涌，研究了水动力作用在锚链上对浮式结构运动的影响。本课题得到的主要结论如下：1)在规则波中进行的两次简调和强迫喘振试验和简调和强迫喘振试验结果表明，在波浪中进行慢漂振荡的TLP模型所受到的粘性阻尼力除了在小减速速度范围内的情况外，都大于静水中进行强迫或自由振荡试验所得到的粘性阻尼力。2)根据相对速度概念得到的阻力系数取决于减速速度。

In the design of mooring systems for a floating ocean structure such as Tension Leg Platform and other type of semi-submersible, the slow drift oscillation is one of the most important problem. In this research project, a fundamental study on the viscous damping forces acting on TLP is carried out by using TLP model and TLP section model. The effects of hydrodynamic forces acting on mooring chains on the motions of floating structure are also researched by comparing the surge of a floating structure moored by chains in irregular waves and that of the structure moored by coil springs.The main conclusions obtained from this research project are as floows:1) Experimental results of two harmonic forced surge tests and the simple harmonic forced surge tests in regular waves shows that the viscous damping forces acting on the TLP model performing the slow drift oscillation in waves are larger than those obtained from the forced or free oscillation tests in a still water except the cases in the small reduced velocity range.2) The drag coefficient obtained on the basis of the relative velocity concept depends on the reduced velocity.