The selection of fishing vessel fleet operations using a multiple criteria optimization method

The methodology adopted in the design of small fishing vessels is usually concerned only with the vessel's technical characteristics and the procedures utilized may not include consideration of the relevant fishing environment. This paper describes an approach which incorporates operational, economic and technical considerations in a compressive manner. The efficiency of using multicriteria decision making methods in design is investigated with special reference to small vessels. A model is presented which takes into account various operational and fish resource factors. This allows the inclusion of a number of potentially conflicting requirements and goals within the design process. The resulting analysis identifies the optimum fleet mix for three types of fishing vessels for use in a fishing environment of a developing country.     

对船检与海事管理中船舶分类的研究

比较船舶检验与海事管理中船舶分类的不同,提出应按照国家标准编制海事系统统一的船舶分类标准。     

Estimation of the response of a deeply immersed cylinder to the shock wave generated by an underwater explosion

The work presented in this paper is focused on the development of a simplified method to study the structural response of a deeply immersed cylinder subjected to the primary shock wave generated by an underwater explosion. The proposed analytical model is based on the string-on-foundation method initially developed by Hoo Fatt and Wierzbicki, who converted the two dimensional boundary value problem of a cylindrical shell to an equivalent one-dimensional problem of a plastic string on a plastic foundation. This method has already been extended by the authors to study the shock wave response of an unstiffened cylinder immersed in shallow water. The present work focuses on deep-immersed cylinders subjected to both high hydrostatic pressure and explosion shock wave. The elastic deformation energy of the cylinder under hydrostatic pressure is first calculated and used to determine the initial conditions of the dynamic problem. Cylinder deflection and plastic deformation energy are then calculated for various immersion depths. When confronted to numerical results, the proposed model appears to underestimate the increase of deflection and absorbed energy with the immersion depth. A thorough analysis of the results post-processed from Ls-Dyna/USA finite element simulations highlights a new mechanism which is due to the action of hydrostatic pressure that continues to push inward the immersed cylinder. In order to improve the analytical model, a correction factor on the hydrostatic pressure is introduced but it is finally concluded that a new mechanism dedicated to the late action of the hydrostatic pressure still needs to be developed.     

采用Rankine源、RANSFS组合方法求解计及波影响的船舶粘性绕流问题

本文开发了边界单元(Rankine源)方法与RANSFS方法相组合求解计及船波影响的船舶粘性绕流问题的切合在微机上实施的方法.对S60(Cb＝0.6)船模,在Fn＝0.316, Rn＝106之下进行了计算验证.对边界单元法中Z＝0面上网格的划分,提出了一种不同的网格划分思想,算得了令人满意的波高分布.对这一组合方法的收敛性进行了较为仔细的考察.总阻力系数Ct的计算值,与测量值的相对偏差达到＜5%.对波高的考察显示,粘性对波的影响主要集中在船体表面附近.     

新波浪理论在系留船舶二阶波浪力计算机中的应用研究

通常在计算波浪与结构物相互作用时都采用规则波假定,例如Airy波和Stokes波,波高一般采用实测有效波高,这种方法认为所有的波浪能量都集中在一个波浪频率上,从而忽视了海洋波浪实际的宽谱特征使得计算出的结构物动态响应不具有代表性.该文阐述了新波浪理论(NewWave Theory)的基本概念,介绍了一种新型的极限入射波浪模型,该模型考虑了天然海浪的随机性、潜性和方向性.新建立的波浪模型不仅可以作为恶劣海域海工结构计算时最不利波浪力设计标准,而且可使系留船舶的全向二阶波浪力计算得到极大的简化,节省大量的时间成本.文中还阐述了新波浪理论模型引入到波浪与结构物相互作用水动力计算的方法和步骤.最后对一种萨哈林(Schiehllion)型FPSO在不同方向入射波作用下的平均漂流力进行了计算和讨论.     

船舶在波浪中航行时沿船体纵向布置齿轮机构的机械效率

船舶在波浪中航行时船体的总弯曲变形会使沿船体纵向布置齿轮机构的轴承支座中心距产生缩减。在一定条件下,这种中心距缩减会导致互相啮合的两齿轮间产生附加的径向压力,从而使齿轮机构处于双面啮合工作状态。本文分析及计算了齿轮机构在该双面啮合工作状态时由齿间摩擦及轴承摩擦所消耗的功率,并以此为依据推导出船舶在波浪中航行时沿船体纵向布置齿轮机构机械效率的计算公式。     

利用Haskind源格林函数计算规则波中航行舰船的绕射兴波及压力分布

在微幅波假定下,以Wigley数学船型为研究对象,利用无限水深三维移动脉动源(Haskind源)格林函数及面元法,建立规则波中顶浪航行舰船的绕射兴波波形及压力分布的计算模型;实现Haskind源格林函数中奇点的积分处理,并编制计算程序进行验证;最后对舰船的绕射波形及压力场分布进行分析。     

On the numerical accuracy of the wave load distribution on a ship advancing in short and steep waves

Defining numerical uncertainty is an important part of the practical application of a numerical method. In the case of a ship advancing in short and steep waves, little knowledge exists on the solution behaviour as a function of discretisation resolution. This paper studies an interface-capturing (VOF) solution for a passenger ship advancing in steep (kA = 0.24) and short waves (L _w /L _pp = 0.16). The focus is to estimate quantitative uncertainties for the longitudinal distributions of the first–third harmonic wave loads in the ship bow area. These estimates are derived from the results of three systematically refined discretisation resolutions. The obtained uncertainty distributions reveal that even the uncertainty of the first harmonic wave load varies significantly along the ship bow area. It is shown that the largest local uncertainties of the first harmonic wave load relate to the differences in the local details of the propagating and deforming encountered waves along the hull. This paper also discusses the challenges that were encountered in the quantification of the uncertainties for this complex flow case.     

新波浪理论在系留船舶二阶波浪力计算中的应用研究

通常在计算波浪与结构物相互作用时都采用规则波假定,例如Airy波和Stokes波,波高一般采用实测有效波高,这种方法认为所有的波浪能量都集中在一个波浪频率上,从而忽视了海洋波浪实际的宽谱特征使得计算出的结构物动态响应不具有代表性。该文阐述了新波浪理论(NewWave Theory)的基本概念,介绍了一种新型的极限入射波浪模型,该模型考虑了天然海浪的随机性、谱性和方向性。新建立的波浪模型不仅可以作为恶劣海域海工结构计算时最不利波浪力设计标准,而且可使系留船舶的全向二阶波浪力计算得到极大的简化,节省大量的时间成本。文中还阐述了新波浪理论模型引入到波浪与结构物相互作用水动力计算的方法和步骤。最后对一种萨哈林(Schiehallion)型FPSO在不同方向入射波作用下的平均漂流力进行了计算和讨论。     

Simulation on progressive collapse behaviour of whole ship model under extreme waves using idealized structural unit method

To ensure the safety of navigating ship, working loads and structural load-carrying capacity are two important aspects. In the present paper, a total simulation system combing load calculation and structural collapse analysis is applied to simulate progressive collapse behaviour of a single-hull Kamsarmax type bulk carrier. A three dimensional singularity distribution method is adopted to calculate pressure distribution with time history. A mixed structural model, collapse part simulated by ISUM elements and remaining part by elastic FEM elements with relative coarse mesh, is proposed for collapse analysis. Progressive collapse behaviour obtained by ISUM is good agreement with that by nonlinear software package, MARC. However, the calculation time of ISUM analysis is about 1/70 of MARC analysis. The applicability to structure system, high accuracy and sufficient efficiency of ISUM had been demonstrated.     

一种小型船舶上排维修装置设计

船舶上排方式很多,根据吨位的不同一般采取不同的上排方式,文章主要针对小型船舶维修保养需要,设计了一种能够减少人工工时,又能够使船舶快捷安全上排的装置,完成船舶后续维修保养工作。     

某冷藏运输船有效功率的爱尔法估算分析

针对某冷藏运输船更换调距桨叶时需预先确定船体有效功率的问题,用爱尔法对弗劳德数、方形系数、爱尔系数和船体有效功率进行估算.文章介绍该冷藏船的主要参数;分析爱尔法估算船体有效功率的原理、计算表达式和爱尔标准船型参数;计算该冷藏船标准方形系数、爱尔系数,并根据实船方形系数、船宽比、浮心纵向坐标和水线长与标准值的差异分别修正...     

水线源强消弃法在船舶定常兴波计算中的应用

当采用等强度源汇分布法求解线性船舶水动力学问题时,船体的水线源强必须等于零,基于这一假定,杜双兴在基于边界元法的数值计算中,令水线附近面元上的源强为零,且水线积分项也自动消失,称这种方法为"水线源强消弃法".本文应用Kelyin移动兴波源格林函数,研究水线源强消弃法在定常航行船舶的兴波计算中的应用,首先以潜航椭球体为例,对Kelvin移动兴波源格林函数进行了计算和验证,然后分别采用常规面元法和水线源强消弃法,对Wigley船型的兴波阻力、波形及船体压力分布进行了计算及试验比较,另外为了考查水线源强消弃法的工程实用性,最后对一艘SWATH船型的兴波阻力进行了计算.结果表明:与考虑水线单元和水线积分的常规面元法相比,水线源强消弃法能够较好地消除水线积分时格林函数的奇异性所引起的误差,给出的预报结果与试验值吻合更好;另外水线源强消弃法的预报结果受网格划分形式、忽略水线单元尺寸大小的影响,文中的算例表明:忽略10%-15%吃水以上的水线单元能够给出较为合理的预报结果.     

数值水池短峰不规则波模拟研究

基于粘性数值波浪水池技术,对短峰不规则波进行数值模拟.文中首先改进了长峰不规则波的数值模拟方法,并使用改进后的方法进行了不同海况下长峰不规则波数值模拟,模拟效果明显改善,数值模拟结果与目标值储吻合相当好.之后进行了短峰不规则波的数值模拟,模拟结果与特征值/目标谱也相当接近.     

近距离船舶无线移动交互信号传输方法研究

传统近距离船舶无线移动交互信号传输方法能够完成交互信号的传输,但受环境干扰因素响应大,为此提出近距离船舶无线移动交互信号传输方法研究。采用无线射频交互信号传输方式,利用相位补偿模块进行高稳态的射频信号传输;依托无线交互信号链路设计,完成交互信号的编码译码设置,从而实现近距离船舶无线移动交互信号传输。实验数据表明,该设计方法较传统设计方法综合响应时间提升24.44%,且具有较高的传输稳定性。     

Breaking wave at the bow of a fast displacement ship model

We investigated the flow structures under the bow wave generated by a fast displacement ship model (INSEAN model 2340) in the presence of wave breaking. The data acquired were also used for a detailed database for CFD validation. The mean and r.m.s. point-wise values of the wave height were measured by means of a finger probe. The intensity of the breaking wave was taken as the r.m.s value of the wave height. The mean velocity field under the free surface was measured at 0.15 L _PP and 0.2 L _PP downstream of the fore perpendicular by means of a 5-hole Pitot probe. Uncertainty assessment of the wave height and velocity field results was performed following the AIAA Standards S-071-1995. Preliminary CFD results from a RANSE code with a breaking model are shown in comparison with the measured data.     

Three-dimensional numerical analysis of shipping water onto a moving ship using a particle method

The objective of this study was to develop a numerical analysis method based on the moving particle semi-implicit method for simulating shipping water on a moving ship. Towing tests of a very large crude carrier were numerically analyzed for three typical wavelengths. The ship was forced to move in order to express previously measured ship oscillations, and the calculated fluid behavior and the impact pressure on the deck were compared with the experimental results.     

Extension of the super-elements method to the analysis of a jacket impacted by a ship

The aim of this paper is to present a simplified analytical method for estimating the crushing resistance of an oblique cylinder impacted by the stem of a striking ship. The collision angle of the vessel is arbitrary, i.e. oblique collisions are also considered in this article. The two extremities of the tube are assumed to be clamped. These developments are intended to be used for evaluating the crashworthiness of an offshore wind turbines jacket. To achieve this goal, closed-form expressions are first derived for the particular situations of a horizontal and a vertical cylinder by applying the upper-bound method. An interpolation formula is then proposed to get the resistance opposed by the tube for any inclination angle. In order to validate these theoretical developments, some comparisons are made with the results of numerical simulations. These latter are performed using the finite elements software LS-DYNA. In almost all cases, the analytical prediction of the resistance is found to be in quite good agreement with the numerical ones. Finally, another comparison is made by simulating an OSV collision with a full jacket. In this case, the theoretical model is found to be insufficient for large impact energies and points out the need of further research.     

Virtual hull monitoring of a naval vessel using hindcast data and reconstructed 2-D wave spectra

A novel virtual hull monitoring approach is assessed using full-scale measurements from a naval vessel trial to address two questions. First: Can this technique accurately reproduce stress spectra from measured strains? Second: Are responses calculated using reconstructed two-dimensional wave spectra from hindcast data more accurate than those using simpler wave representations? Stresses calculated using wave hindcast data, ship track information, and stress transfer functions compare favorably to those derived from strain gauge measurements at five structural locations. Wave conditions are represented using a spectrum model along with bulk spectral parameters (significant wave height, peak period, and primary direction) from hindcast datasets and by reconstructing two-dimensional spectra from hindcast partition data. Both approaches give good agreement with strain measurements but using the more-detailed reconstructed two-dimensional wave spectra yields better results. Results suggest that wave hindcast data are sufficient for accurate structural calculations, encouraging further study of virtual hull monitoring using wave hindcast data.