Low-frequency damping of a moored semisubmersible obtained from simulated extinction tests and mean wave drift forces

Low-frequency damping of a moored semisubmersible drilling platform was obtained from numerical extinction tests simulated in still water and in regular waves and from mean wave drift forces calculated at zero forward speed. The influence of drag forces was represented by the modified Morison equation. The platform as used for the 18th ITTC Comparative Mooring Study was analyzed in irregular beam waves. The computed time series of sway as well as the corresponding sway response spectrum compared favourably with model test measurements, demonstrating that this procedure to determine low-frequency damping can be effective.     

Motion and Dynamic Responses of A Semisubmersible in Freak Waves

The present research aims at clarifying the effects of freak wave on the motion and dynamic responses of a semisubmersible. To reveal the effects of mooring stiffness, two mooring systems were employed in the model tests and time-domain simulations. The 6-DOF motion responses and mooring tensions have been measured and the 3-DOF motions of fairleads were calculated as well. From the time series, trajectories and statistics information, the interactions between the freak wave and the semisubmersible have been demonstrated and the effects of mooring stiffness have been identified. The shortage of numerical simulations based on 3D potential flow theory is presented. Results show that the freak wave is likely to cause large horizontal motions for soft mooring system and to result in extremely large mooring tensions for tight mooring system. Therefore, the freak wave is a real threat for the marine structure, which needs to be carefully considered at design stage.     

Multi-Objective Optimization of A Semisubmersible for Ultra-Deep Water

Semisubmersible will work well when oil exploitation goes to ultra-deep water because of its variable load capacities, and good motion performance in extreme waves. It is considered to be a main type of platform while the water depth is more than 3000 meters. This paper establishes a multi-objective optimization model of semisubmersible for ultra-deep water, and it is solved by a multi-objective genetic algorithm--NSGA-Ⅱ. The model is applied to a practical design, and Pareto results are obtained. The effectiveness of the method is verified by hydrodynamic analysis.     

LH11-1半潜式平台的船体-系泊系统测量

深水海洋平台的现场监测是对平台性能的直接评估,对保障平台安全,改进平台设计方法等具有重要意义。介绍在南海LH11-1平台上开展的现场监测工作,内容包括海洋环境、平台运动以及系泊系统测量。对平台在洛坦台风中的运动响应进行了测量结果与分析结果的比较分析。结果表明数值分析结果与测量结果部分吻合,但仍有差异,测量结果的波频分量大于计算结果,但计算的精度在可接受的范围内。     

一种新型半潜式平台概念设计研究

在详细研究影响平台综合性能的诸多因素基础上,克服现有半潜式平台存在的不足,结合自升式平台甲板可以自由升降的优点,开发了具有自主知识产权的自升式半潜多功能深海浮式（JCSM）平台。JCSM平台结合了自升式平台与半潜式平台的优势,并以平台综合性能的提升为目标进行了细节上的优化,稳性裕度大且运动性能优良,可适应干式采油、湿式采油和干湿组合式采油等不同采油模式,并同时具有钻井、早期生产、修井、油气处理与油气储运等多种功能。在详述JCSM平台的组成及性能特点的基础上,对JCSM平台进行了稳性与运动性能数值分析,并与传统半潜式平台相比较,验证了所研发新型平台性能的优越性。研究为未来海洋油气田开发提供了一种新的选择,并对全新概念的浮式平台开发有借鉴和指导意义。     

横轴半潜式潮流能发电装置设计与试验研究

为了促进深远海养殖装备朝智能化方向发展,解决电能供给困难的问题,克服抗风浪网箱受波流耦合作用对太阳能和风能利用的局限性的问题,针对养殖区域的低流速海域,提出了一种适用于深远海可升降网箱的横轴半潜式潮流能发电装置,建立了Savonius型水轮机叶片受力数学模型,分析了叶轮中心与水面的距离对水轮机捕能效率的影响,利用Fluent软件数值模拟了导流增速浮体的速度场情况,设计了发电装置整体结构及锚泊系统,搭建了发电装置试验模型,开展了物理模型试验,测试了不同水流速度情况下与叶轮相对离水距有关的各参数变化情况,并对试验数据进行分析。试验结果表明,在不同的水流流速下,随着离水距的不断增加,捕获功率呈先增加后减小的趋势,当叶轮中心高出水面1/4个叶轮直径时,叶轮的输出功率最大。