船舶与海洋工程毕业设计外文翻译.doc

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 JapanAbstract: Since 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 Ikeda，s 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 proposed.Key words: Roll damping, simple prediction formula, wave component, eddy component, bilge keel component.Introduction In 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 6，7 with the computer program. The prediction method, which is now called Ikedas method, divides the roll damping into the frictional (BF), the wave (Bw)，the 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 (kgfm)/roll angular velocity (rad/sec) can be expressed as follows:B44Bbk (1) At 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 used.For 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 8.Previous Prediction Formula The 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 high.From 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 revised.Methodical Series Ships Modified 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 equations.Proposal of New Prediction Method of Roll Damping In 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 developed.As 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 damping.reason 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 theory.Conclusions A 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, B/d, Cb，Cm, OG/d, G)，bBK/B, Ibk/Lpp，(pa, 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 study.References五、 Y. 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 Japanese)六、 Y. 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 Japanese)七、 Y. 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 Japanese)八、 Y. 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 Japanese)九、 Y. Himeno, Prediction of Ship Roll Damping一State of the Art, Report of Department of Naval Architecture & Marine Engineering, University of Michigan, No. 239, 1981.十、 Y. Ikeda, Prediction Method of Roll Damping, Report of Department of Naval Architecture, University of Osaka Prefecture, 1982.十一、 Y. Ikeda, Roll damping,in: Proceedings of 1stSymposium of Marine Dynamics Research Group, Japan, 1984, pp. 241-250. (in Japanese)十二、 Y. 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, 2008，pp. 79-86.十三、 Y. 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 Japanese)十四、 N. Tanaka, Y. Himeno,Y. Ikeda, K. Isomura,Experimental 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6,7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，B/d, Cb，Cm, OG/d, G)，bBK/B, Ibk/Lpp 。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 Vessels on Feb 21st, the industry was shocked by the news that AP Moller-Maersk placed an order of 10 container ships of 18,000 TEU with the South Korean ship yards. The order brings the development of large vessels to a new climax 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 etc.In 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 vessels”，however, 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 relative.In 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 industry,shipping industry and related industries.At present, the industry pays close attention to the development of large vessels and at the same time the safety of ships.Chen Yongnian from R&D 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 devastating.In traditional theory，the 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 lot of unknown factors affecting the safety of ships. Therefore, in the development of large vessels, it will be inevitable to have some safety problems. Like the nuclear plant accident in Japan, when they first built the plant, they did not predict that such accident could happen in the future. They could only make the solution they considered best and establish corresponding standards and rules in the light of the existing technical conditions and backgrounds. In fact, shipbuilding industry is the same. Though the technical solutions have become advanced and varied, there are still many uncertainties as to whether the existing experience and ability can cope with the development of large vessels.大型船舶的限制2月21日，被业界震惊的消息，AP穆勒 - 马士基集团下订单的10与韩国造船厂18,000 TEU集装箱船。该订单使大型船舶发展到了一个新的高潮，并在同一时间提出了一系列研究对象，如发展大型船舶的极限是什么，是否可以保证船舶安全等。 就目前的发展趋势，大型船舶，江南造船（集团）公司总工程师有限公司胡先生科艺认为，从理论和技术的角度来看，大型船舶的发展是没有问题的，即使有问题，发展船舶的大小是由许多因素决定，如通道，港口，码头的深度和船东揽货能力。因此，这种“无限大”是相对的。在每一段时间中，大型船舶的发展面临着许多制约因素。然而，从历史的发展（尤其是集装箱船），每个限值“专家预测已被一个