Study On Hydrodynamic Characteristics And Motion Stability Of Spar Platform

There exists most of the oil and gas which makes up30percent of the total resource indeep water in South Sea. According to the practical observation and relative research, it isfound that there exits strong coupled effects between heave and pitch. So it is very importantto do some study on motion stability and coupled nonlinear motion characteristic of Sparplatform. The main contents of this article are below:1. The calculation methods of wave loads of every part of Spar platform are introduced,and then the motion equation of Spar platform is created in frequency domain. The results ofwave loads and motion responses of Spar platform are given by WALCS and compared withthe results obtained by SESAM. The responses of Spar platform in irregular wave are given.2. The simplified model of Spar platform is created, and then the restoring force andmoment of Spar platform in still water are obtained according to the varied initial metacentricheight and displacement volume. The coupled motion equation between heave and pitch iscreated.3. According to the parametrically excited Mathieu equation, the Mathieu instability withboth little and large parameter excitation of Spar platform for pitch motion is studied,including the influence caused by linear and nonlinear damp. Some research on the stabilityof the solution of Mathieu equation.4. After the coupled motion equation between heave and pitch is created, the heaveresonance phenomenon of Spar platform is studied. And then according to the nonlineardynamic theory, the saturation phenomenon, amplitude jump phenomenon and the stability ofthe coupled heave-pitch movement are studied when the heave primary resonance occurs tothe Spar platform, and some correlative engineering advice is raised.