Mooring System And Wave Forces Of Spar Platform

Spar platform is a new type of offshore oil platform, since it has excellent motionbehavior and relatively low cost, it soon became one of the most popular platform indeep ocean. This article thoroughly discusses the development of the Spar platform.Then, do further research into the mooring system and the second-order diffractionproblem, and develop two softwares to solve the mooring stiffness matrix and thedifference-frequency wave load on a Spar platform.The main parts of this paper are shown as follows:1. According to the variation of the structure designs of Spar platform, we dividedthe Spar platforms into three generations, and emphasized on the structure design,motion behavior and economy characristics of each generation of Spar, introduce theSpar platform into China ocean engineering industry.2. Establish an analysis modle of the Spar mooring system, based on the catenaryequations, also computed the length changes in the mooring line uncer variable linetension, the nonlinear mooring forces of multi-component catenary mooring lines arecaculated by an iterative procedure controlled by tolerable error, and then got themooring stiffness matrix of Spar platform. Developed two computer software namedSEMA and MMEA, which can calculate the single line mooring force and thestiffness matrix of the whole mooring system. And use these softwares to compute theforce-excursion relationship of a four lines moored Spar platform in different intialhorizontal force conditions, shown the influences of the intial horizontal force to themooring stiffness.3. The Spar can be simplified as a large diameter, truncated cylinder, we focus onthe diffraction problem in bichromatic incident waves, and the boundary integralequation method is applied. Introduce the ring-source Green function and establish aFredholm integral equation of the second kind to solve the difference-frequencypotential, and a efficient method to compute the free surface integral, then theequation is caculated by BEM. Finally solved he difference-frequency force QTFs..