An introduction to hull design practices for deepwater floating structures

The concepts of floating structure plays a very important role in deepwater projects; and the design of the floating structure is one of the most important tasks in the project. The importance of the floating structure in offshore projects can be demonstrated in the following several areas： the substantial dynamic structure responses due to wave loading and current loading; the limited motion requirements of risers in deep water; and the increasing difficulty of installation for different components of the system. Three major technical aspects have to be considered, i.e. the strength of structure, the fatigue resistance capacity of the system, and local and global stability of the structure. This paper reviews the current design practice of floating structures, evaluates the main tasks during the design and associated major technical requirements, and addresses the major technical challenges encountered during the design. As a close-out of the paper, the authors discuss some potential future developments in the design of floating structures.

新型浮式生产系统的开发和研究

讨论了一种新型浮式生产系统的开发和研究.该系统具有潜在的市场开发经济性和可行性,特别是对深海及远海石油天然气的开发.新型的浮式生产系统是一种BMFPSO系统(Buoy Moored Floating Production Storage and Offloading system),该系统应用一个垂直的浮式圆柱取代传统的应用在FPSO上的转塔(turret)系统且仍具有风标效应.BMFPSO的船体在风、浪、流的作用下可以围绕垂直的浮式圆柱作360°的旋转.浮式圆柱可以设计在船体内(或船体外)的悬臂中.除此之外,船体还可以沿着垂直的浮式圆柱作垂向移动,从而消除了传统的转塔式FPSO纵摇和垂荡耦合运动,减小了系统在极端海况以及正常作业情况下锚泊线及立管的张力.由于BMFPSO具有以上特征,采油树布置在平台上的干式立管系统和常规的钢管悬链线立管可以在BMFPSO上得到应用,从而使得立管系统的投资和维修更加经济和方便.除此之外,BMFPSO系统也可以用来作为液化天然气终端.

南海腐蚀环境下三体船结构典型节点疲劳特性研究

针对南海腐蚀海域中航行三体船的疲劳寿命进行了研究.基于腐蚀指数模型确立了三体船在南海环境中0 a、10 a、15 a及20 a时的腐蚀厚度,并基于谱分析方法进行疲劳累计损伤度计算和疲劳寿命分析.通过对不同腐蚀期限的计算结果分析表明,考虑腐蚀板厚折减的疲劳寿命计算方法可能使其疲劳寿命减少30%以上.

A fully nonlinear and weakly dispersive water wave model for simulating the propagation,interaction,and transformation of solitary waves

This paper presents the development of a theoretical model of fully nonlinear and weakly dispersive(FNWD)waves and numerical techniques for simulating the propagation,interaction,and transformation of solitary waves.Using the standard expansion method and without the limit of small nonlinear parameter defined as the ratio of the wave height versus water depth,a set of model equations describing the FNWD waves in a domain of moderately varying bottom topography are formulated.Exact solitary wave solutions satisfying the FNWD equations are also derived.Numerically,a time-accurate and stabilized finite-element code to solve the governing equations is developed for wave simulations.The solitary wave solutions of FNWD,weakly nonlinear and weakly dispersive(WNWD),and Laplace equations based models in terms of wave profile and phase speed are compared to examine their related features and differences.Investigations on the overtaking collision of two unidirectional solitary waves of different amplitudes,i.e.,ax and a2 where a1>a2,are carried out using both the FNWD and WNWD water wave models.Selected cases by running the FNWD and WNWD models are performed to identify the critical values of a1/a2 for forming a flattened merging wave peak,which is the condition used to determine if the stronger wave is to pass through the weaker one or both waves are to remain separated during the encountering process.It is interesting to note the critical values of a1/a2 obtained from the FNWD and WNWD models are found to be different and greater than the value of 3 proposed by Wu through the theoretical analysis of the Korteweg-de Vries(KdV)equations.Finally,the phenomena of wave splitting and nonlinear focusing of a solitary wave propagating over a three-dimensional semicircular shoal are simulated.The results obtained from both the FNWD and WNWD models showing the fission process of separating a main solitary wave into multiple waves of decreasing amplitudes are presented,compared,and discussed.