船舶与海洋工程毕业设计外文翻译.doc

船舶与海洋工程毕业设计-外文翻译 毕业设计论文外文翻译 题 目 7500吨干货船技术设计 总体方案及第三部分 专 业 船舶与海洋工程 班 级 学 生 指导教师 重庆交通大学 2013年A Simple Prediction Formula of Roll Damping of Conventional Cargo Ships on the Basis of lkedas Method and Its LimitationYuki Kawahara Kazuya Maekawa and Yoshiho IkedaDepartment of Marine System Engineering Osaka Prefecture University Sakai 599-8531 JapanSince the roll damping of ships has significant effects of viscosity it is difficult to calculate it theoretically Therefore experimental results or some prediction methods are used to get the roll damping in design stage of ships Among some prediction methods Ikedas one is widely used in many ship motion computer programs Using the method the roll damping of various ship hulls with various bilge keels can be calculated to investigate its characteristics To calculate the roil damping of each ship detailed data of the ship are needed to input Therefore a simpler prediction method is expected in primary design stage Such a simple method must be useful to validate the results obtained by a computer code to predict it on the basis of Ikedas method too On the basis of the predicted roll damping by Ikedas method for various ships a very simple prediction formula of the roll damping of ships is deduced in the present paper Ship hull forms are systematically changed by changing length beam draft mid-ship sectional coefficient and prismatic coefficient It is found however that this simple formula can not be used for ships that have high position of the center of gravity A modified method to improve accuracy for such ships is proposedKey words Roll damping simple prediction formula wave component eddy component bilge keel componentIntroductionIn 1970s strip methods for predicting ship motions in 5-degree of freedoms in waves have been established The methods are based on potential flow theories Ursell-Tasai method source distribution method and so on and can predict pitch heave sway and yaw motions of ships in waves in fairly good accuracy In roll motion however the strip methods do not work well because of significant viscous effects on the roll damping Therefore some empirical formulas or experimental data are used to predict the roll damping in the strip methods To improve the prediction of roll motions by these strip methods one of the authors carried out a research project to develop a roll damping prediction method which has the same concept and the same order of accuracy as the strip methods which are based on hydrodynamic forces acting on strips The review of the prediction method was made by Himeno 5 and Ikeda 67 with the computer program The prediction method which is now called Ikedas method divides the roll damping into the frictional BF the wave Bwthe eddy Be and the bilge keel Bbk components at zero forward speed and at forward speed the lift Bi is added Increases of wave and friction components due to advance speed are also corrected on the basis of experimental results Then the roll damping coefficient B44 roll damping moment kgfmroll angular velocity radsec can be expressed as followsB44Bbk 1At zero forward speed each component except the friction and lift components are predicted for each cross section with unit length and the predicted values are summed up along the ship length The friction component is predicted by Katos formula for a three-dimensional ship shape Modification functions for predicting the forward speed effects on the roll damping components are developed for the friction wave and eddy components The computer program of the method was published and the method has been widely usedFor these 30 years the original Ikedas method developed for conventional cargo ships has been improved to apply many kinds of ships for examples more slender and round ships fishing boats barges ships with skegs and so on The original method is also widely used However sometimes different conclusions of roll motions were derived even though the same Ikedas method was used in the calculations Then to check the accuracy of the computer programs of the same Ikedas method a more simple prediction method with the almost same accuracy as the Ikedas original one has been expected to be developed It is said that in design stages of ships Ikedas method is too complicated to use To meet these needs a simple roll damping prediction method was deduced by using regression analysis 8Previous Prediction FormulaThe simple prediction formula proposed in previous paper can not be used for modem ships that have high position of center of gravity or long natural roll period such as large passenger ships with relatively flat hull shape In order to investigate its limitation the authors compared the result of this prediction method with original Ikedas one while out of its calculating limitation Fig 1 shows the result of the comparison with their method of roll damping The upper one is on the condition that the center of gravity is low and the lower one on the condition that the center of gravity is highFrom this figure the roll damping estimated by this prediction formula is in good agreement with the roll damping calculated by the Ikedas method for low position of center of gravity but the error margin grows for the high position of center of gravity The results suggest that the previous prediction formula is necessary to be revisedMethodical Series ShipsModified prediction formula will be developed on the basis of the predicted results by Ikedas method using the methodical series ships This series ships are constructed based on the Taylor Standard Series and its hull shapes are methodically changed by changing length beam draft midship sectional coefficient and longitudinal prismatic coefficient The geometries of the series ships are given by the following equationsProposal of New Prediction Method of Roll DampingIn this chapter the characteristics of each component of the roll damping the frictional the wave the eddy and the bilge keel components at zero advanced speed are discussed and a simple prediction formula of each component is developedAs well known the wave component of the roll damping for a two-dimensional cross section can be calculated by potential flow theories in fairly good accuracy In Ikedas method the wave damping of a strip section is not calculated and the calculated values by any potential flow theories are used as the wave dampingreason why viscous effects are significant in only roll damping can be explained as follows Fig 4 shows the wave component of the roll damping for 2-D sections calculated by a potential flow theoryConclusionsA simple prediction method of the roll damping of ships is developed on the basis of the Ikedas original prediction method which was developed in the same concept as a strip method for calculating ship motions in waves Using the data of a ship Bd CbCm OGd GbBKB IbkLpppa the roll damping of a ship can be approximately predicted Moreover the limit of application of Ikedas prediction method to modern ships that have buttock flow stern is demonstrated by the model experiment The computer program of the method can be downloaded from the Home Page of Ikedas Labo AcknowledgmentsThis work was supported by the Grant-in Aid for Scientific Research of the Japan Society for Promotion of Science No 18360415 The authors wish to express sincere appreciation to Prof N Umeda of Osaka University for valuable suggestions to this studyReferencesY Ikeda Y Himeno N Tanaka On roll damping force of shipEffects of friction of hull and normal force of bilge keels Journal of the Kansai Society of Naval Architects 161 1976 41-49 in JapaneseY Ikeda K Komatsu Y Himeno N Tanaka On roll damping force of shipEffects of hull surface pressure created by bilge keels Journal of the Kansai Society of Naval Architects 165 1977 31-40 in JapaneseY Ikeda Y Himeno N Tanaka On eddy making component of roll damping force on naked hull Journal of the Society of Naval Architects 142 1977 59-69 in JapaneseY Ikeda Y Himeno N Tanaka Components of roll damping of ship at forward speed Journal of the Society of Naval Architects 143 1978 121-133 in JapaneseY Himeno Prediction of Ship Roll Damping一State of the Art Report of Department of Naval Architecture Marine Engineering University of Michigan No 239 1981Y Ikeda Prediction Method of Roll Damping Report of Department of Naval Architecture University of Osaka Prefecture 1982Y Ikeda Roll dampingin Proceedings of 1stSymposium of Marine Dynamics Research Group Japan 1984 pp 241-250 in JapaneseY Kawahara Characteristics of roll damping of various ship types and a simple prediction formula of roll damping on the basis of Ikedas method in Proceedings of the 4th Asia-Pacific Workshop on Marine Hydrodymics Taipei China 2008pp 79-86Y Ikeda T Fujiwara Y Himeno N Tanaka Velocity field around ship hull in roll motion Journal of the Kansai Society of Naval Architects 171 1978 33-45 in JapaneseN Tanaka Y HimenoY Ikeda K IsomuraExperimental study on bilgekeel effect for shallow draftship Journal of the Kansai Society of Naval Architects 180 1981 69-75 in Japanese常规货船的横摇阻尼在池田方法基础上的一个简单预测方法及其局限性Yuki Kawahara Kazuya Maekawa and Yoshiho Ikeda海洋系统工程部酒井599-8531日本大阪府立大学摘要由于船的横摇阻尼对其粘度有显着的影响所以很难在理论上计算因此某些实验结果或某些预测方法都被用于一般的设计阶段在这些预测方法中池田方法被广泛应用于许多船舶运动的计算机程序使用这个方法可以对含有各种舭龙骨的船体进行计算从而探讨其不同的特性为了计算每个船的横摇阻尼详细的数据也是必须的因此在设计初期就需要更为简便的预测方法方法虽然简单但也得通过电脑程序的验证并证明在池田方法的基础上是有用的在这个基础上推导出的简便公式就是现在的这个在本文件船体形式的变化是通过改变船长船宽吃水中横剖面系数及棱形系数来等来等到然而这个简化公式不能用于具有较高的重心位置的船所以一些改进的方法以提高准确行就应运而生了关键词横摇阻尼简单的预测公式波分量涡分量舭龙骨组件介绍 在20世纪70年代以来船舶在波浪中的运动已发展成了具有5个自由度的运动形式新的预测方法已经建立该方法是基于势流理论Ursell-Tasai 方法源分布法等可以预测间距升沉摇摆及波浪中船的偏航运动并都有不错的精度然而在横摇运动中带条的方法并适合因为粘性效应对对横摇阻尼有很大的影响所以就需要用一些经验公式和实验数据来检验这些公式 为了提高这些带钢方法预测横摇运动的准确性作者之一就就开发了一些项目来发展这个横摇预测方法而这些都是基于水动力带条方法都有相似的概念和顺序精确度也能够保证预测方法是由姬野5和池田67的计算机程序审查 预测的方式现在叫池田方法被分为了零航速阻尼的摩擦BF波浪BW涡流BE和舭龙骨BBK组件前进的速度升降机Bi在校正实验结果的基础上推进速度的波和摩擦部件增加 前进速度为零各组成部分之外的摩擦和电梯部件的每个横截面单位长度预测预测值总结了沿船的长度摩擦成分预测由加藤的公式为一个三维的船舶形状预测横摇阻尼元件的前进速度的影响的修改功能的开发的摩擦波浪和涡流组件这个方法的计算机程序也已经开发出来了并被广泛的使用 30年间原始池田方法开发传统船舶已被该进以适用于多种船舶例如更加修长和方形的船舶渔船驳船带有尾鳍的船等等原来的方法也被广泛使用但是有时横摇运动的不同的结论即使来自相同池田的方法在计算中使用然后判断是否相同池田的方法与几乎相同的精度池田原来一直期望开发一种更简单的预测方法的计算机程序的准确性有人说在船舶设计阶段池田的方法太复杂使用为了满足这些需求使用回归分析推导出一个简单的横摇阻尼预测方法 以前的预测公式 前文中提出的简单的预测公式不能用于的调制解调器船舶有高重力或自然卷长期间如大型客船船体形状相对平坦的中心位置为了研究它的局限性作者比较的结果这种预测方法与原池田之一而其计算限制实验结果与他们的方法的横摇阻尼最上层在重心低的情况下下面那层是在低重心的情况下 从这个数字看这个公式估计的结果与池田公式对低重心船的估计结果很好的吻合对高重心船会有误差实验结果表明以前的预测公式需要被修改成型的系列船 修改的的公式可以用成型的系列船型来发展成为池田公式的预测结果该系列的船是在泰勒船型的基础上建立的通过对他的船长船宽吃水中横剖面系数及纵向棱形系数来实现减摇预报的新方法建议 本章中每个组件的一些特性如横摇阻尼摩擦波浪力涡流和舭龙骨组件都是在静水中讨论并得出的简化公式众所周知二维横截面的波分量可以通过势流理论精确的计算在池田的方法中条状横截面的兴波阻尼不能计算得到而通过势流理论得到的计算值曾经一直被使用因为粘性效应值在横摇阻尼有如此的重要性结论 在池田原预测方法的基础上这是相同概念作为一个条法计算船舶运动波的方式并用船舶横摇阻尼开发的一个简单预测方法用到的数据Bd CbCm OGd GbBKB IbkLpp 此外模型实验证明了池田的预测方法特别是在现代船舶的用途上但有一定的限制The limit of Large Vesselson Feb 21st the industry was shocked by the news that AP Moller-Maersk placed an order of 10 container ships of 18000 TEU with the South Korean ship yards The order brings the development of large vessels to a new cli and at the same time puts forward a series of research subjects to the industry such as what is the limit for the development of large vessels whether ship safety can be guaranteed and etcIn relation to the current development trend of large vessels the chief engineer of Jiangnan Shipbuilding Group Company Ltd Mr Hu Keyi believes that from the perspective of theory and technology there is no problem with the development of large vessels even with the development of infinitely large vesselshowever the size of ships is limited by many factors such as channels ports wharf depth and the ability of cargo collection of shipowners Therefore such infinite largeness is relativeIn every period of time the development of large vessels faces many constraints However as seen from the history of development in particular container ships each limit value predicted by experts has been broken one by one This gives an enlightenment to the industry on one hand development of large vessels can not ignore the constraints of practical conditions on the other hand it can not be restricted by the practical conditions In today when science and technology are developing at a fast speed nothing is impossible The excellent performance of AP Moller-Maersk and South Korean ship yards in the area of container ship is a good example which is deserving more attention and research from Chinas port industry shipbuilding industryshipping industry and related industriesAt present the industry pays close attention to the development of large vessels and at the same time the safety of shipsChen Yongnian from RD center of CCS thinks that though there are the preconditions in terms of theory and technology for the development of large vessels the issue of safety cannot be underestimated Since the accidents involving these Big Macs will be devastatingIn traditional theorythe ability of withstanding waves will get stronger with the increase of the size of ships However we should be fully aware that human beings havent fully grasped the factors which affect vessels strength and safety in particular the history of the development of large vessels is not long and data accumulated is relatively limited the safety of large vessels hasnt been verified in many aspects and there are still a lo