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Article type: Cover
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Cover1-
Published: March 30, 1975
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Article type: Cover
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Published: March 30, 1975
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Masaaki KUROI, Matao TAKAGI, Ryusuke HOSODA, Momoyo TAKAHASHI
Article type: Article
Pages
1-9
Published: March 30, 1975
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A calculation of optimum ship route is carried out by using the data of sea condition experienced by a high speed single-screw container ship, the "Kashu-Maru". The effectiveness of the calculation method is verified by comparing the calculated results with the records of the "Kashu-Maru". Simulation of navigation in the North Pacific Ocean is also made and the problems awaiting improvement are discussed about the calculation method of optimum ship route.
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Katashi TAGUCHI, Yoshisada MUROTSU, Takashi HONJO
Article type: Article
Pages
11-20
Published: March 30, 1975
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This paper is concerned with a problem to select an optimum fleet size to serve a transport demand at an arbitrary route with one port loading and one port unloading. The quality of a fleet size is considered to be judged on the transport costs and the service qualities. An optimization problem is set up for determining the optimum fleet size to minimize the weighted sum of the transport costs and the service qualities. Basic mathematical models relating the transport costs and the service qualities to a fleet size, i.e., the number of ships, the pay load and the service speed, are developed for a case of tankers. Tci llustrate the validity of the proposed optimization problem and the mathematical models, an optimum fleet size is determined in an arbitrary selected tanker route, under the assumption that the transport demand is fixed. The effects of the various factors, such as variations in the length of voyage, the mathematical models, etc. on the optimum fleet size are briefly discussed.
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Hisayoshi TATANO, Yoshitsugu YAMAZAKI, Masanobu SUDO, Mitsuhiro ABE
Article type: Article
Pages
21-30
Published: March 30, 1975
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This report presents the results of a number of steering tests of two free-running, self-propelled tanker models with several rudder configurations including the attachment of a Kort-nozzle. 1) Model A with a l/57 relative size rudder shows an abnormally stable character in straight running and this is emphasized by fitting the smaller rudders against expectation. 2) Model B with a l/63 rudder shows an unstable loop and the smaller rudders result in the wider unstable loops as one may expect. 3) By fitting a Kort-nozzle for these two models which have typically different characters, r'∼δ curves around origin are shifted to bring worse course stabilities for any size of rudders. The nozzle affects the stable model much and the unstable one less. 4) At ballast conditions of model A, almost same characters are obtained whether with a nozzle or not and irrespective of rudder area. But when the largest l/57 rudder is fitted, the model shows slightly better response for both cases of that with and without nozzle. 5) For improving course stability, it has been thought that increasing of rudder area is the simplest way for usual stern form ships but in case of model A, the better characters are provided by the smaller rudders. Even in the case with a nozzle, slightly better effects are obtained by cutting the upper part of a l/57 rudder. In case of model B with a nozzle, the upper part of l/63 rudder has no effects on course stability. These facts impress that the upper part of a conventional rudder does not play an important role but sometimes causes bad influences.
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Shoichi NAKAMURA, Ryusuke HOSODA, Shigeru NAITO
Article type: Article
Pages
31-43
Published: March 30, 1975
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With a ship model of single-screw high speed container ship, resistance and selfpropulsion tests in regular and irregular head waves were carried out in the Experiment Tank of Osaka University. The experimental results of ship motions and resistance increase in regular head waves are compared with the results obtained from the theoretical calculations. The significant amplitudes of heave and pitch and the mean increases of resistance, propeller thrust, torque and revolution measured in irregular waves are compared with the values which are predicted from the response operators obtained by the experiments in regular waves and the wave spectra by applying the linear spectral method. The self-propulsion factors in regular and irregular waves are analysed by assuming that the mean characteristics of a propeller are identical with those in still water.
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Shoichi NAKAMURA, Kimio SAITO, Yoshio ISOZAKI
Article type: Article
Pages
45-55
Published: March 30, 1975
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In order to study the hydrodynamic pressure on ship's hull travelling in waves, model experiments have been continued with an ore carrier model. In this report the following problems are discussed, comparing the results of experiment with those of theoretical calculation based upon the ordinary strip method : (1) Effect of the difference between the actual form and the Lewis form section, which is used for the calculation by the ordinary strip method, on the amplitude of the hydrodynamic pressure. (2) Applicability of the linear superposition technique in order to estimate the amplitude of the hydrodynamic pressure in irregular waves. (3) Analysis of the amplitude of the hydrodynamic pressure at the points near the waterline.
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Susumu HIRANO, Kazuhiro FUKUDA
Article type: Article
Pages
57-65
Published: March 30, 1975
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Many researchers have presented various theories of boundary layer in unsteady flow. However they seem to have been confined to problems of laminar boundary layer. It is interesting to know how a turbulent boundary layer responds to the process of deceleration of the body. This paper is concerned with an experimental investigation in the phenomenon of decelerating a flat plate uniformly in towing condition, as one of the most simple case. The following remarks. become known from this experiment. (1) A secondary boundary layer is formed from the back edge of the flat plate in the field of the initial boundary layer. (2) Momentum thickness of the initia boundary layer is increased by the growth of the secondary boundary layer, while the shape factor (ratio of displacement thickness and momentum thickness) is not changed. (3) During the process of constant deceleration, the viscous drag has just smaller value than that of steady case at any instantanous velocity, but the difference of them is too small to make a clear distinction.
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Masanori SUGIURA, Hiroshi ISSHIKI
Article type: Article
Pages
67-74
Published: March 30, 1975
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The water wave problem of oscillating bodies, which has the so-called Sommerfeld's radiation condition on a fictitious boundary placed in a finite distance from a body, is investigated. First, the uniqueness of the solution for the problem is generally demonstrated and the Green function is obtained. Then, making use of this Green function, the solution is shown to approach to that of the original problem when the fictitious boundary tends to infinity, and also, numerical investigation is carried out to estimate the appropriate location of the boundary. Finally, this investigation is examined in the hydrodynamic coefficients of a circular dock computed by the finite element method.
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Toshiho GOTO, Sestuji MINEHISA, Haruo AKANE, Akira ANDO, Daijiro MATSU ...
Article type: Article
Pages
75-86
Published: March 30, 1975
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Copper-alloy has long been well used for the sleeve of propeller shaft, because of its superior corrosion-resistance. But in recent years international shortage of copper resource has brought unstable conditions of its supply and its price. Under these circumstance the following are now in consideration, that is to use another alloy, supply of which is stable or to employ another construction which needs less amount of copper-alloy. And this sleeve, when some damages occur, is very difficult to be repaired by welding because it is made of Sn-bronze, and it takes much time to replace the damaged sleeve. This situation have brought a new idea, that is to use the stainless steel overlay shaft, instead of a combination of the steel shaft and the sleeve made of Sn-bronze. This new stainless steel overlay type has several advantages compared with the sleeve type, as shown below. (a) It is easily repaired by welding when the sleeve is damaged (b) This method can reduce a machining process in manufacturing. Paying attention to this point, we has carried out a basic study including selection of materials for welding and investigation into its fatigue strength, and has performed an experiment by equipping a trial produced propeller shaft to Yoshino-Maru. As a result the followings have been made clear. (1) The overlay shaft with austenite stainless steel 316L showed twice as good endurance as old copper alloy sleeve (BC-2 or BC-3) (2) We can improve work efficiency and get a product with sufficient quality by adopting band arc submerged arc welding method. (3) The fatigue limit of stainless overlay shaft in seawater was improved to be 25 kg/mm^2 by practicing surface rolling. (4) Through the two years experiments on actual ship we could get good results finding no problem in view of corrosion and wear, and obtained data applicable to actual ships.
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Hiroshi KUROKOCHI, Yoichi HARA, Hiroyuki YAMADA, Yasunori KOGA, Sadao ...
Article type: Article
Pages
87-95
Published: March 30, 1975
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In estimating reaction force at the supporting blocks in repair dry docks, not only keel blocks but also side blocks should be taken into consideration in the case of large ships. For the analysis of the problem usual way of analysis regarding the ship as single beam on an elastic foundation is invalid. The authors developed a general purpose computor program for the analysis of two-dimensionally arranged supporting blocks. Several calculations by this computor program revealed general characteristics of load allotments by keel and side blocks. Based on the calculated values the quantitative relations between the load allotments and misalignments of block heights and, furthermore, the handling principle of automatic blocks were obtained.
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Yoichiro OKAMURA, Ken-ichi KITAURA, Yoshio FUKUMOTO
Article type: Article
Pages
97-103
Published: March 30, 1975
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Pulsating tension tests on structural models of mild steel, H-section with circular holes in the web, were carried out ; S-N curves were obtained, and the effect of the flange size and the radius of the circular hole on the fatigue strength was clarified. Furthermore, the effect of stress concentration factor and stress gradient on the fatigue strength based on crack initiation was discussed.
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Matao TAKAGI, Koji HARADA, Seiichiro MURATA, Masaaki KUROI, Toru HORI, ...
Article type: Article
Pages
105-123
Published: March 30, 1975
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Theoretical formulae are derived for stresses in the tank structures of a ship among the irregular waves under the following assumptions : i) The stresses in the tank structures are not affected by the deformation of the main structure of the ship. ii) The angular velocities about the center of gravity of the tank, that due to the rotational motions of the ship, do not affect the pressure which acts upon the wall of the tank. The formulae obtained under the above assumptions show that the stresses are non-linear functions of the three components of the acceleration at the center of gravity of the tank. The statistical characteristics of the irregular stresses are investigated by a numerical simulation method. The following results are obtained : i) The statistical distributions of the time serries of the stress are nearly equal to the normal distribution. Their means and variances can be estimated by equations (E・7), (E・8), (E・17) and (E・18) in Appendix E. ii) The statistical distributions of the maxima and amplitudes are nearly equal to Cartwright & Longuet-Higgins's and Ochi's truncated ones respectively. Based upon the above results, a method is proposed for the statical prediction of the irregular stresses.
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Article type: Appendix
Pages
125-130
Published: March 30, 1975
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Article type: Appendix
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Published: March 30, 1975
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Article type: Appendix
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Published: March 30, 1975
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Article type: Appendix
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Published: March 30, 1975
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Article type: Cover
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Published: March 30, 1975
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