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Article type: Cover
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Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Article type: Index
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Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Article type: Index
Pages
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Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Shigeyuki OGINO, Yoshitaka HASHIMOTO
Article type: Article
Pages
1-7
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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As one of the ways of increasing fuel economy for full single-screwed ships, this paper presents newly developed asymmetric stern, which features that stern end before propeller is shifted from ship's center plane. Shifting distance is maximum at propeller boss around, and gradually reverts to the center as going up & downwards. The model experiments were carried out for panamax size BC with this shape and the necessary power of full scale was estimated by using newly proposed self propulsion analysis method. The results show about 7% energy saving can be expected by use of this stern.
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Jia FU, Qian HONG
Article type: Article
Pages
9-17
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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In this paper, fishing vessel, fishing ground and fishing port are looked upon as a system, and that the influence of "uncertainties" are considered into this system. The economic analysis is made for ice trawler as an example. Authors point out that realizing optimum vessel type under the variation of some "uncertainties" is difficult, but the "satisfactory" design can be obtained. Therefore, the condition of "satisfaction" can be kept on economic nature for fishing vessels under the variation of different "uncertainties". This paper proposes the method and the steps while considering the influence of "uncertainties". It also suggests that the principle of the method and the steps of treatment can be applied into technical and economical evaluation of other vessel types for specification of hull, machinery and equipments (i.e. owners requirements).
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Kazuo SUZUKI
Article type: Article
Pages
19-24
Published: March 25, 1989
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Minimization of the theoretical wave resistance is one of the most important themes in our study field. Minimum wave resistance theory given by Maruo and Bessho, which is based on the thin ship theory, is very useful for the practical hull form design. However this theory can not be extended to other new complicated wave theories which were proposed in recent years, because the wave resistance is minimised by means of the classical variational method. In the present paper, theoretical wave resistance based on the low speed theory is minimised by means of the nonlinear programming under given design constraints. Numerical examples are given for several cases and model tests involving the towing test and the wave analysis are carried out. The usefulness of the low speed theory for the hull form design are confirmed.
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Wusheng SONG
Article type: Article
Pages
25-32
Published: March 25, 1989
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The numerical method to the new slender ship theory is described for calculating the flow around a slender ship with a steady drift angle. The study of this paper is in only the wave-making problem. The method of representing the ship by sources distributed over the surface of the hull is utilized here, and the densities are determined by solving Volterra integral equation of the second kind on the basis of the approximate hull boundary condition due to the assumption of the slender body. The velocities are directly obtained from numerical differentiation of the total velocity potential in three axis directions. Then, wave-making resistance, lateral force and yaw moment acting on the ship at various Froude numbers are computed by integrating pressure on the hull surface. In order to investigate the relationship between the ship wave change and the drift angle, the wave patterns are calculated for several drift angles. All above calculations are based on the marching integration, so it is seen that such a numerical procedure is in a sense efficient to numerical ship hydrodynamics. The Wigley model is used in the present calculation. From the comparison of calculated and measured ship waves, the pratical application of the theory is examined further.
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Akira KAKUGAWA, Yukio TAKEI, Haruya TAKESHI, Toshifumi HORI
Article type: Article
Pages
33-39
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Investigations were made on the Laser Doppler Velocimeter (LDV) measurement in a towing tank especially with regard to the seeding technique and traversing of an optical unit. The longitudinal velocity component of the flow, on the propeller disk plane of a pure car carrier, was measured in a towing tank using a small fiber optic LDV. The water and aluminium powder mixture was injected as seeding, from the front of bow of the model ship into the flow field, and the data rate reached 10∼300 counts per second. The comparison with the 5-hole Pitot tube results showed that the wake contour with LDV is similar but slightly wider than that with Pitot tube.
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Yuji HASEGAWA, Taketoshi OKUNO, Reiji YAMASAKI, Yuji NAKANISHI, Hisao ...
Article type: Article
Pages
41-46
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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In order to make a basic design concept of electro-magnetic log arrangement on high-speed ship, flow field around fore bottom is investigated experimentally and numerically. To clarify the characteristics of fore bottom flow field at incidence, measurement of velocity distributions by use of 3-hole pitot tube and flow visualization are carried out. Velocity distributions in real ship at both ahead and steady turning conditions are also measured by changing log depth. It is pointed out that boundary layer thickness at ahead, longitudinal vorticies caused by separation of flow and deformation of boundary layer at incidence should be taken into consideration for log arrangement. The comparison between the calculated boundary layer parameters by Okuno's method on 3-D turbulent boundary layer and the measured one shows good agreement even on high-speed slender ship.
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Shigeru NISHIO, Yoshinori NORITAKE, Ichiro TANAKA
Article type: Article
Pages
47-54
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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The separated flow field around prolate spheroid at small incidence is investigated experimentally. The measurement of the surface pressure distribution and the flow visualization are carried out. From the results of the flow visualization, surface stream pattern and the position of the separation line are obtained, and saddle points exist on the separation line of the side. Several flow patterns are observed near rear end by careful consideration of the flow field near symmetric plane. All of those flow patterns are consistent topologically with the flow which has saddle points on the separation line of the side. The results of the surface pressure distribution are considered with the results of the flow visualization. It is found thet the effect of longitudinal vortex component grows strong as the angle of attack increases, the flow pattern obtained from pressure distribution and the flow pattern obtained from visualization are consistent.
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Kazumi SUGAWARA, Kenjirou MIKI, Ryuichi SATO
Article type: Article
Pages
55-62
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Japan Foundation for Shipbuilding Advancement (Chairman R.Sasakawa) is planning to build a full scale experimental ship of superconducting electromagnetic propulsion. The thruster of the ship consists of six ducts placed on circumference of a circle and each of them is surrounded with a pair of superconducting coils and has a pair of electrodes inside. The thrust is generated by lorentz force due to interaction of the magnetic field and electric current in sea water going through the ducts. The present design of the ship puts the thruster inboard. The sea water therefore is led from an intake at the bow and flows into the thruster after divided into six branches at a junction. The sea water then increases in pressure in the thruster and flows into a duct at a combining junction to spout out from a nozzle at the stern. Development of junctions of low loss coefficient will provide high propulsive performance for the ship. Few reports however are found on the loss of junctions of multiple branches. The present paper deals with the tentative design of the junctions of six branches and measurement of pressure loss of the junctions with their models.
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Ryuichi SATO
Article type: Article
Pages
63-67
Published: March 25, 1989
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A supercavitating propeller with thin blades for a small racing boat is made of pure titanium by precise molding. Open water and cavitation test results are compared with those of thick-bladed brass propeller which has the same particulars except blade thickness. Efficiency of the titanium propeller is higher about 8.5% than the brass propeller. The titanium propeller generates supercavitation more easily than the brass propeller, because of its sharp leading edges.
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Makoto UCHIDA, Eiichi NISHIKAWA, Noboru NAKAI, Hideo KAMIYAMA, Hikaru ...
Article type: Article
Pages
69-75
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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On the occasion of the building of new training ship "FUKAE MARU" of Kobe Mercantile Marine University, an attempt was planned to measure the blade stress of her controllable pitch propeller. She has the overall length of 50 meters, the displacement of 449 tons, and the CPP with diameter of 2.1 meters and with skewed angle of 40 degrees. The propeller and the shaft were designed and constructed to be able to install the measuring apparatus, which consists of the data processing component, the frequency-multiplexed telemeter kit, the cables through the propeller shaft connecting the leading wires of strain gauges with the telemeter kit, and the strain gauges put on the blade surfaces. The most sensitive parts of the apparatus are the gauges and the flexible cables crossing the boundary between the movable blade and the propeller boss, those whitch are exposed to the severe water flow. Much laborious efforts were payed to search the appropriate the sticking and coating materials of gauges, and the durable flexible cable. Measurement trials were carried out over the certain ranges of blade angle and propeller revolution number. According to the trial results, (1) the blade stress of CPP can be measured reliably by the method developed here, (2) the blade stress varies corresponding to the wake distribution, so that it fluctuates cyclically with the propeller revolution, (3) the mean stress changes in proportion to the mean propeller thrust, on the other hand, the fluctuating amplitude shows the different behaviour from that of the mean stress.
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Hisao TANAKA, Katsuya NAKATA
Article type: Article
Pages
77-82
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Recently, there is a large demand of wave generators for leisure pool facilities. For the wave-generators in the facilities, it is most important performance that they can make large waves suitable for surfing. The authors formerly developed a water-head type wave generator which can make large solitary waves. The authors also predicted maximum wave height based on conservation low of mass, but the result was unreasonable. Regarding the wave generator as a kind of energy transformation system, the authors have predicted maximum wave height. Consequently, the prediction results of wave height have showed good coincidence with experimental results. Efficiency of energy transformation also has been investigated experimentally.
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Seiji TAKEZAWA, Tsugukiyo HIRAYAMA, Kiyoshi MIYAKAWA, Takehiko TAKAYAM ...
Article type: Article
Pages
83-95
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Recently, the directional spectrum water wave generator for long tanks has been developed and established at the Experimental Tank of Yokohama National University, (Length 100m, Breadth 8.0m, Water draft 3.5m). 16 unit wave generators were installed on a short wall of the long tank. This wave generating system is based on a new concept to generate the specified directional spectrum water waves. Reflection of waves on the sidewalls, that has been always recognized as a bad phenomenon for a good wave generation, is utilized positively for generating the specified directional spectrum waves to propagate in the long tank. For this new system, the unit wave generator, the electronic control system and soft wares for wave generating signals were newly developed in Yokohama National University. By the use of this system, successful directional spectrum waves were obtained in the almost all zone of the long tank on both lengthwise and widthwise. It means that the running model test in specified directional spectrum waves is possible. On the other hand, the generation of directional spectrum waves by this system is restricted to have the symmetric directional spreading function and propagate along by the long tank.
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Kimio SAITO, Matao TAKAGI, Hisato SHIKIDA, Hisafumi YOSHIDA
Article type: Article
Pages
97-106
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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This study deals with the impulse response of a horizontal circular cylinder. Forced and free oscillation tests in a still water were performed. The technique for identifying the memory effect function from the measurements are reviewed both in the time domain and frequency domain. The memory effect function is transformed to corresponding frequency dependent hydrodynamic coefficients of a cylinder using the Fourier transform and they are compared with the solutions of a radiation problem. The obtained results are compared with the analytical solution and the validity of the identification methods is discussed.
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Yoshikazu YAMAMURA, Yoshiho IKEDA, Norio TANAKA
Article type: Article
Pages
107-114
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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In order to evaluate Morison equation with constant coefficients, measurements of the hydrodynamic viscous forces acting on irregularly oscillating circular cylinders and flat plates, which are deeply submerged, are carried out. Constant drag and mass coefficients are obtained for each process by frequency domain analysis using spectra as well as time domain analysis. The obtained coefficients by the two methods are different from each other. Moreover, the frequency domain analysis is valid in a region of very limited Keulean-Carpenter number. And it is confirmed that the error of the predicted value by Morison equation with the obtained constant coefficients increases with Keulegan-Carpenter number, because of variety of vortex shedding of every swing. This suggests that hydrodynamic coefficients varying from swing to swing should be used for accurate prediction of viscous forces acting on an oscillating blunt cylinder.
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Yasuo YOSHIMURA, Hitoshi SAKURAI
Article type: Article
Pages
115-126
Published: March 25, 1989
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Turning and course keeping qualities significantly change according to the water depth. In the previous reports, the author presented the predicting techniques of the manoeuvring ship motion both in deep and shallow water for a single-propeller single-rudder ship. Meanwhile, the investigation into the manoeuvrability and its predicting method for a twin-propeller twin-rudder ship are also desired, because such kind of ships are widely adopted to wide-beam or blant ships as well as high-speed ships. However, it may be said that the inadequate experimantal or theoretical researches can be seen for these ships. In shallow water, the turning qua1liy of some wide-beam and twin-propeller twin-rudder ship are unexpectedly improved, though the conventional ships usually become the worse in the shallower water depth. In this report, the manoeuvrability and its predicting techniques for a twin-propeller twin-rudder ship are investigated by means of conducting the captive model tests and digital simulations with different two twin-propeller twin-rudder ships. Through the present study, the following conclusions are obtained. 1) The presented methematical model based on MMG's model is available for the manoeuvring prediction of a twin-propeller twin-rudder ship both in deep and shallow water. 2) The mathematical model and the measured hydrodynamic data show that the mechanism of shallow water effects on rudder force is quite different from those on hull damping force. The rudder force depends upon the hull resistance and propulsive performance, while the hull damping force upon the effective aspect ratio of hull. 3) As the turning quality is produced by the balance of yaw moments which are induced by two forces as mentioned above, the stronger hull damping force makes the worse turning quality in shallow water, and the stronger rudder force the better one like the presented wide-beam ship. 4) One of the important factors to improve the turning quality in shallow water is the reduction of propulsive effeciency. For this purpose, additional ship stopping devives such as spoiler, fin or water parashot may be usefull.
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Naoya UMEDA, Yasuyuki YAMAKOSHI
Article type: Article
Pages
127-137
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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This paper presents results of circular motion tests with large drift angles for a stern trawler under manoeuvring at low speed. The hull form used is longitudinally non-symmetric and differs from hull forms ever investigated in previous works. Since the non-symmetry emphasizes defects of previous mathematical models, a mathematical model is developed for both longitudinally non-symmetric and symmetric ships. Hydrodynamic lateral force and yaw moment are assumed to consist of two components, that is, forces caused by cross flow effect and lift forces affected by stall effect. Local drag coefficients in conventional models are regarded as a polynomial of longitudinal ordinate x. They cannot explain experimental values under towing abeam, or are beyond rational values as steady-state drag coefficients. To bypass this difficulty, we regard local drag coefficients as a quadric form of longitudinal ordinate x and yaw rate r. These coefficients explain the cross flow effect for the trawler and a car carrier, and are within rational values as steady-state drag coefficients. Derivatives of the lift forces are determined from three experimental conditions where drift angles are 0,90 and 180 degrees. The derivatives coincide with theoretical values derived from a slender body theory. Stall effect is simply approximated by change in the derivatives of the lift forces. As a whole, values approximated for the lateral force and yaw moment agree with experimental values. In addition, experimental values of longitudinal force and heeling lever due to the lateral force from water surface for the trawler are presented.
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Tetsuo OKADA, Hiroshi SASAJIMA, Isao NEKI
Article type: Article
Pages
139-146
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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This paper proposes a method of r-type mesh optimization for the finite element analysis of two dimensional elasticity problem. The objective function of the optimization is the global error energy norm based on stress discontinuity on the element boundaries. The mesh generation is based on the method to generate boundary-fitted coordinate systems as solutions of biharmonic equation in the physical plane. Computer codes were developed and some examples were investigated. It is shown that the approach to the optimized mesh in this paper is effective and useful for practical use.
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Hajimu MANO, Hiroshi KAWABE, Kouji MASAOKA, Kiyoto HAYAKAWA
Article type: Article
Pages
147-155
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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This report is concerned with sound transmission through a panel constructing ship structure. There are two courses of sound transmission of panel. The one is out of plane vibration of panel, the other is in plane vibration. We show that the principal element of the transmission is caused by out of plane vibration. We formulate a coupled vibration of panel-sound medium interaction by using both boundary conditions, making use of the B.E.M. for panel and sound medium. As a numerical example, we calculate the sound transmission loss through a circular panel in an infinite rigid baffle. We discuss the relation between transmission loss and panel stiffiness and material. We clarify that the tendency of transmission depends on the frequency of the incident sound. For a low frequency vibration, the dominant element of transmission is by panel flexural vibration mode, so that the transmission loss increases with flexural rigidity of panel. For a high frequency range, property of transmission can be explained by the mass law.
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Tadao YAMANO, Hodaka SHIMIZU
Article type: Article
Pages
157-166
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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The mechanism and the effect of a new vibration reduction system are presented. The system reduces surface force with the effect of an air layer in a tank and openings at a hull. On the basis of the pressure measurement in a circulating water tank, a simple calculation model was introduced to estimate the effect of the system on vibration reduction. The calculation model allowed the authors to design the system for a ship. In addition, resistance and self-propulsion tests were conducted in a towing tank, yielding the results that the system hardly gave any influence on propulsion performance. Sea Trials on two car carriers yielded that the system was effective to reduce ship vibration caused by surface force.
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Shohei YOSHIDA, Hajime KAWAKAMI, Naoki YAMANAKA, Ryoichi OHMINAMI, Hir ...
Article type: Article
Pages
167-177
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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Large concrete offshore structures have been constructed so far in one united body in a large graving dock. However, this method needs a large amount of capital investment for building a graving dock beforehand. On the other hand, if we could use an existing shipbuilding dock, which is fully equipped, we will be able to enjoy much economical advantage for the production of such a concrete offshore structure, in time and cost. But, the existing shipbuilding dock is not wide enough to allow a large concrete offshore structure to be constructed in one body. To overcome this problem, we have developed a method for joining afloat concrete offshore structure sections which have been built in two in an existing shipbuilding dock. In this method, the joint is located at the center part of the structure where the maximum resultant forces act and there exist some structural discontinuities. We have calculated the ultimate strength of the joint using FEM analysis and confirmed that the joint has strength comparable with other parts which have been constructed beforehand in a shipbuilding dock.
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Masakazu KAJI, Koichi OKAMOTO, Hiroshi YAMASHITA, Tetsuro IKEBUCHI
Article type: Article
Pages
179-188
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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On a high-speed hydrofoil catamaran of hybrid-type whose weight is supported by lift of hydrofoils and buoyancy, only a few studies have been made about calculation method of the wave force and relation between the wave force and the structural response. Then to investigate the applicability of a strip method (STFM) considering the interference between two lower hulls, the authors carried out a model experiment in waves and compared the results with the calculated ones. The authors executed 3-D FEM calculations and clarified the relation between the characteristic global hydrodynamic responses and structural responses, influence of the hydrofoils on the total strength, and influence of the motion control on the strength.
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Hironobu HASHIGUCHI, Shinichi OHTANI, Shinichi TODA
Article type: Article
Pages
189-195
Published: March 25, 1989
Released on J-STAGE: April 01, 2018
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In the design work of ship's propulsion shafting, the designing methods, investigating items, etc. have been so much established that CAE (Computer-Aided-Engineering) is easily applicable. The authors have recently developed a comprehensive design system "KSHAFT" applicable to the entire shaft design process from the initial to the detailed stage, and which was the following main components: 1) data-base of shafting design. 2) shafting particulars determination program. 3) function calculation programs, and 4) drawing programs. They are linked by a unified data file. The "KSHAFT" has been proven in use with an increase in design efficiency, etc.
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Article type: Appendix
Pages
App1-
Published: March 25, 1989
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