【作者】 赵文斌；

【导师】 唐友刚；

【作者基本信息】 天津大学 ， 船舶与海洋结构物设计制造， 2007， 硕士

【摘要】 本文研究深海Spar平台的波浪载荷和水动力系数,以及平台垂荡-纵摇耦合运动的马休稳定性问题。研究工作对于深海Spar平台的设计和开发具有重要的意义。由于平台的结构特点,纵摇的回复力系数是平台排水量和纵摇初稳性高的函数,平台垂荡时排水量和初稳性高也随时间变化,因此平台的垂荡和纵摇耦合运动为可以用参数激励方程表示。当Spar平台有较大的垂荡运动,且平台垂荡运动频率和纵摇固有频率满足2:1内共振关系时,纵摇运动出现马休失稳。当马休不稳定出现时,垂荡运动能量向纵摇传递并显著的加大纵摇运动幅值。对于主体波浪力的求解,文中用半解析方法研究孤立的截断的浮式Spar平台主体的一阶绕射问题,在Matlab平台上编制了波浪力计算程序。程序可以计算在不同波浪入射角时的纵荡激励力、垂荡激励力和纵摇激励力矩。对于水动力系数的求解,理论上用半解析方法研究了孤立截断浮式Spar平台主体的一阶辐射问题,推导了一阶辐射速度势的计算公式,在Matlab平台上开发了Spar平台主体水动力系数计算程序。程序可以求解纵荡附加质量系数、纵荡附加阻尼系数、垂荡附加质量系数、垂荡附加阻尼系数、纵摇附加质量系数和纵摇纵荡附加阻尼系数。两个程序得到的数值计算结果与WAMIT等软件计算结果一致。因此可应用于Spar平台的运动计算。文中运用集中质量方法模拟锚链,并编制了锚链和平台的耦合运动计算程序。研究结果表明:平台的垂荡运动对于波面升高最为敏感;纵摇阻尼对于平台纵摇运动的稳定性起到了非常重要的作用;锚链对抑制纵摇失稳作用显著,但它不直接作用在纵摇上而是通过减小平台的垂荡运动幅值来影响纵摇稳定性。更多还原

【Abstract】 The objectives of this study are to obtain wave loads and hydrodynamic coefficients for Spar platform and to evaluate heave-pitch coupling motion and Mathieu instability, which are referable in design and fabrication of spar platform.According to the characteristic of Spar, the pitch restoring coefficient can be represented by a function of the displaced volume and the metacentric height of Spar. Due to heave motion, the displaced volume and the metacentric height of Spar platform change in time and this heave-pitch coupling can be represented by parameter excited equation. Mathieu instability for a Spar platform arises when there is large heave motion and the period of the heave motion is half of the pitch natural. In the process, kinetic energy is transferred from heave mode to pitch and the amplitude of pitch is magnified considerably.For wave exciting force, the main body of the Spar platform is simplified as an isolated truncated float vertical cylinder. An exact semi-analytical method is described to solve one order diffraction problem of Spar platform and a computer program is developed for obtaining surge, heave wave exciting force and pitch wave exciting moment in different wave heading. For hydrodynamic coefficients, using the same simplified model, one order radiation problem of Spar platform is in detail deduced by using semi-analytical method in theory and also a computer program is developed for obtaining the added mass and damping coefficients of surge, heave and pitch respectively. The two Calculation program ware compiled using Matlab software. Comparisons between the numerical results given in the paper and those obtained from MOSES and WAMIT show excellent agreement. The results can be used for calculating motion of Spar. The mooring is simulated by lumped mass model and coupled with the hull of Spar to evaluate the motion of Spar by a coupled program.The results in this paper show that the wave elevation effect is the main reason for inducing heave motion and the pitch damping coefficient significantly affects the Mathieu instability. The results also show that mooring effect can suppress the Mathieu instability by reducing the heave amplitude but not directly function on pitch.更多还原