Comparison of the mariner Schilling rudder and the mariner rudder for VLCCs in strong winds

A simulation model of a very large crude carrier (VLCC) with either a mariner type Schilling rudder or a mariner rudder was developed from captive and free-running model tests. Kijima’s regression formula was used to predict the hydrodynamic hull forces on the VLCC. To simulate full-scale maneuvering at cruising speed, the constant torque operation of the main engine was assumed. Considering the higher normal lift force and maneuverability of the mariner type Schilling rudder as compared to the mariner rudder, the size of mariner type Schilling rudder is kept smaller as compared to mariner rudder. To compare the efficiency of the two types of rudder system, maneuvering simulations at constant engine torque and course-keeping simulations at various gusting wind speeds and encounter angles were carried out. Based on the simulation results, the two rudder types were compared from the viewpoint of maneuvering and fuel efficiency in windy conditions.     

玄武岩纤维材料在酸、碱性环境下的耐久性试验研究*

为了解玄武岩纤维本身的耐酸、耐碱性能,对其在80℃2 mol/L盐酸和氢氧化钠溶液中腐蚀不同周期后的质量变化、单丝强度进行了试验研究,并与聚丙烯纤维、耐碱玻璃纤维的耐酸碱性进行了对比。结果表明,在耐酸性能方面,玄武岩纤维最优,其次是聚丙烯纤维,耐碱玻璃纤维表现最差;在耐碱性能方面,表现优劣依次为聚丙烯纤维、玄武岩纤维和耐碱玻璃纤维。试验结果为玄武岩纤维新材料在水泥混凝土中的推广应用提供参考。     

强风下有帆商船航行性能的研究

Ships which have large structures above water surface, such as pure car carriers (PCCs) and container vessels, have large speed reduction by wind pressure. In the present study, the running speed of a large PCC with two or more sails for using wind power is simulated. The simulated results demonstrate that the ship can keep a constant service speed even in winds of 20m/s except head and bow winds. This sail system can shorten annual average navigation time by about 4 hours per voyage.     

航母编队装备体系的效能模型研究

将航母编队装备视为一个装备体系进行分析,使用串联、互补、协同3种结构要素,分析了航母编队装备体系的体系结构。根据航母编队装备体系结构和各组成装备效能,建立了评估装备体系效能的数学模型。算例表明此数学模型具有一定的有效性。     

舰船装备技术保障指挥能力评估研究

舰船装备技术保障指挥能力评估是一项重要工作.首先详细介绍了评估原则,在分析舰船装备技术保障指挥能力主要影响因素的基础上,构建了评估指标体系.针对评估指标的模糊性,建立了基于模糊综合评判的评估模型,给出了详细计算步骤.该方法通过将初始评估数据逐层综合,最后得到总的评估结果.该模型计算简单,适用性强,能够较好地解决评估中的模糊性问题,可为舰船装备技术保障指挥能力评估提供方法支持.     

长江下游鳗鱼沙浅滩整治工程措施的初步研究

通过分析鳗鱼沙浅滩河床演变规律及其碍航特征,综合考虑各方面因素,确立了浅滩整治原则与思路,并建立扬中河段河工模型,针对浅滩整治工程措施进行了深入的试验研究,共提出三大类整治工程布置方案。研究结果表明,顺应河道自然属性,因势利导地采用稳固江中心滩的整治工程措施,保持稳定的水下分汊河型,使得两侧深槽满足深水航道尺度要求,并符合两岸岸线利用需求,技术可靠且现实可行,也值得其他类似浅滩治理所借鉴。     

流致噪声机理及预报方法研究综述

流激舵系统引起的振动对水下航行体隐蔽性产生较大影响。为深入研究其振动特性,根据舵系统的结构组成进行简化,建立系统二元线性颤振数学模型,确定低速颤振的产生条件,并获得低速颤振的主要影响因素和作用规律。此外,在重力式水洞中开展舵模型流激振动试验,重点研究了支撑刚度、扭转刚度、质心和刚心位置等参数变化对舵模型流激振动的影响。结果表明：在流体载荷激励下,舵系统结构设计对流激振动特性有较大影响,通过对升沉运动与扭转运动频率之比、结构质量与附加质量之比、刚心、质心与弦中心的相对位置等参数进行匹配设计,能够有效抑制舵系统流激振动。     

网络层次分析法在舰船补给能力评估中的应用

舰船补给能力的评估是评价海军海上后勤保障能力的重要组成部分。在充分分析舰船补给能力的层次指标体系的基础上,引入网络层次分析法(ANP)建立了分析评估模型,经过实例的检验,证明了模型和方法的高效性与可行性。     

均流中大型集装箱船桨舵干扰粘性流场的数值计算研究

应用FLUENT软件的滑移网格技术,实现了均匀来流中的桨舵干扰粘性流场计算。考察了桨推力、舵受力,桨舵周围的速度、压力分布。为尝试预报舵空泡性能,还考察了桨舵间距变化对舵面上的压力分布的影响,取得了与舵空泡观察试验一致的结果。本项工作为船后桨舵干扰粘性流场计算提供了基础。     

A two-dimensional response to a tropical storm on the Gulf of Mexico shelf

Surface current data from drifting buoys and remotely sensed wind data recorded over the continental shelf in the northeastern Gulf of Mexico during the passage of tropical storm Josephine in October 1996 are examined. Drifter data show the existence of a strong surface jet (velocities reaching 1 m s⁻¹) that moves up the west Florida shelf and westward along the Louisiana–Texas shelf, and lasts for nearly 1 week. The coastal jet occurs during an intense synoptic scale wind event where wind speeds reach 15 m s⁻¹. A simple force balance and statistical analysis are performed to assess the role of strong wind forcing. The primary balance shows an Ekman-type current. The role of local acceleration is greatest when winds are directed along bathymetry. A simple two-dimensional strongly forced shelf response model developed from the linear steady-state momentum equations also indicates larger along-shore currents due to both Ekman-type forcing by cross-shore winds and a cross-shore pressure gradient arising from conservation of mass. Model parameters fit empirically are within 15% of theoretical values. The simple model explains 30% and 46% of the variance in the observed along-shore and cross-shore surface currents, respectively.     

沿海交通水域测绘行业管理研究

文中在东海海区三个测量案例分析的基础上,指出了沿海交通水域测绘市场中存在的主要问题和原因,并提出了进一步加强海事测绘部门和通航部门合作,规范行业管理的对策建议。     

Study on the maneuverability of a large vessel installed with a mariner type Super VecTwin rudder

The suitability of the Mariner type Super VecTwin rudder (hereinafter, the MSV rudder) for a large vessel is assessed in this article. Several experiments in a maneuvering pond were carried out and their results analyzed and summarized. Free-running tests such as turning, zigzag, and stopping tests were carried out with a 4-m free-running model of a very large crude carrier (VLCC) ship with the MSV rudder and the Mariner rudder. The results were compared to validate the maneuverability of a VLCC-sized a ship installed with the MSV rudder. A mathematical model of an MSV rudder is proposed for maneuvering simulation of a large vessel. To develop a maneuvering simulation for the model ship that was used in the free-running tests, hydrodynamic coefficients were estimated based on Kijima's regression formula. The coefficients of interaction between the hull and rudder (t_R, a_H, x_H) were obtained from a self-propulsion test in a towing tank. The complicated flow around the rudders is simplified to model the flow speed around the rudders. This simplified flow speed is utilized to compare the time histories of the free-running tests with the simulations. The mathematical model of the MSV rudder was further improved using the results of this comparison.     

Grid convergence study in the resistance calculation of a trimaran

As a new type of hull form, trimaran has remarkable excellent performances and has drawn more and more attention. When the viscous CFD technology now available is applied to the research of resistance performance of trimaran, the spatial discretization would usually result in the grid error and uncertainty, and thus the considerable discrepancy between the numerical results and the experimental data. In order to ascertain how much the grid would affect the calculation, the grid convergence should be studied. A mathematical trimaran was chosen as an example, with the commercial code CFX for the simulation, VOF for surface treatment, and the grid study was carried out based on two different turbulence models. It was concluded that carrying out grid study is helpful in estimating the grid error and uncertainty, and indicating the direction of improving the credibility of the numerical calculation, and, in addition to grid errors and uncertainties, the turbulence modeling errors and uncertainties contribute to the simulation errors.     

某双艉鳍船型设计问题的综合治理与效果研究

本文基于某双艉鳍船型在设计中出现的问题,利用CFD的计算技术,深入剖析了该船在实船试航过程中出现的螺旋桨负荷过重、转速不稳定、左右桨转速差别较大,船艉部产生较剧烈的振动、航速同要求值相差甚远,面临弃船边缘的成因。在实船已经建成,船体线型及螺旋桨均无法改动的情况下,通过切割螺旋桨直径及修削随边,设计并加装整流鳍,采用舵球节能装置等三项综合措施后,成功解决了上述诸多问题,取得了极其显著的效果,能得以顺利交船,避免了出现难以估量的重大损失。     

台风对舟山某渔港工程码头波况影响的模拟

采用改进的藤田气压模型计算8114号台风风场,同时采用MIKE21 SW波浪数学模型模拟台风作用下的波浪场。通过数值模型计算,提供码头位置在台风过境时的波浪情况,为工程建设提供依据。计算结果表明：8114号台风期间,工程海域出现12级以上的西北向大风,登步岛码头水域的有效波高大约在2.5 m,西闪岛码头水域约为2.0 m;波浪周期约为4.5 s;登步岛码头和西闪岛码头水域波向均在W—NW向。从8114号台风过境时码头水域的波浪场模拟计算结果可以看出,外海波浪对工程水域影响不明显,工程水域仍受岛上局地风浪影响。     

基于数值模拟的船艏抗气泡性能分析

对船舶静水中航行问题进行了CFD数值模拟,分析了船艏抗气泡性能。为获得船体周围气泡分布规律,在船前来流中添加气泡,并基于拉格朗日描述法追踪气泡的运动。根据计算得到的气泡分布特点,通过修改船艏线型改善了船舶的抗气泡性能。此外,开展了模型试验,通过船体表面的流线验证了数值模拟方法的可靠性。     

e-Navigation发展研究

近年来在IMO主导下,e-Navigation研究方兴未艾。文中结合世界航海技术的发展现状介绍了e-Navigation产生的背景、概念的形成、IMO等国际组织对其发展所起到作用,重点介绍了国际海事界目前在e-Navigation发展方面取得的最新成果,并结合中国海事局现状,对我国e-Navigation的发展提出了相关建议。     

基于改进遗传算法的双体无人艇性能优化分析

基于并行策略遗传算法对双体无人艇性能进行综合优化分析.首先建立以快速性、操纵性、抗倾覆性和耐波性为目标函数的综合优化数学模型,并使用响应面拟合的方法建立了3种不同的阻力数据库,通过遗传算法对其进行优化分析选出一组最适合本文的阻力数据库.在此基础上选取5个设计变量作为敏感变量进行讨论,其中最为敏感的2个变量将进行并行策略...     

船用螺旋桨及桨后发电机设计可行性研究

  目的  以概念船舶节能装置为研究对象,  方法  在船用螺旋桨后布置尾流发电机,利用螺旋桨的高速尾流推动发电机叶轮旋转,从而带动发电机组,将尾流能回收转化为电能,降低船舶的总体能耗。将螺旋桨及海流发电机视作组合推进器一体设计,采用涡格法分析桨的水动力性能,采用原创的改进叶素动量方法评估桨后处于高度非均匀流场中的发电机的性能。采用遗传算法设计最佳的海流发电机叶片几何,为某实船提供设计方案,并通过CFD方法验证方案的性能。  结果  经与原桨比较,结果显示：在进速系数不变的情况下,组合推进器的推力可提高约4%,但收到功率略有增加;如果调整转速,则组合推进器在推力略有损失的情况下可降低能耗3.43%。  结论  计算分析证明了该节能装置的可行性,可作为降速航行的替代方法。     

Systematic study on the hull form design and resistance prediction of displacement-type super-high-speed ships

Systematic theoretical and experimental studies were carried out to establish methods for hull form design, optimum dimension selection, and resistance estimation for displacement-type super-high-speed ships. In this study, a theoretical hull form design method for displacement-type super-high-speed ships was first developed using the minimum resistance theory and a sectionally varying hull form equation. Using an established hull form design method, a series of 60 hull forms were prepared with systematic variations of the most important design variables, and model tests were conducted for these ship models. Finally, regression analyses were performed for the results of the model tests. The study was very successful, and the prepared computer programs are now being actively used as efficient tools for the design of the displacement-type super-high-speed ships.