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Article type: Cover
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Cover1-
Published: June 30, 1988
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Article type: Index
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Toc1-
Published: June 30, 1988
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Article type: Appendix
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App1-
Published: June 30, 1988
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Mitsuo KISHI, Yuichi IISAKA, Yasukazu HIDAKA
Article type: Article
Pages
1-9
Published: June 30, 1988
Released on J-STAGE: April 01, 2018
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One of the most important considerations when developing a design code based on reliability concept lies in the choice of target reliabilities (or allowable failure probabilities) for the structure/elements. The choice is generally made by a process of probabilistic calibration to existing design codes. There are various feasible designs which satisfy the design code ; therefore, it is expected that lifetime reliabilities corresponding to those designs will be distributed with large spread. In this study, the reliabilities corresponding to the minimum weight design within the specified constraints of the design code are interpreted as the target reliabilities, and the algorithmic procedure is proposed for the evaluation. The proposed procedure is applied to the calibration of API (American Petroleum Institute) PR2A, a design code for fixed offshore structures, whose fatigue design criteria for tubular joints were revised on basis of structural reliability analysis of level 2.
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Hideaki MIYATA, Gazi Md. KHALIL, Young-Gill LEE, Makoto KANAI
Article type: Article
Pages
11-23
Published: June 30, 1988
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Nonlinear interactions between water waves and horizontally submerged cylinders (circular as well as rectangular) are experimentally investigated. The horizontal and vertical components of the forces acting on a single cylinder are measured at various depths of submergence. In the twin cylinder case, the forces acting on the rear cylinder are measured at various spacings and depths of submergence. The results are analysed and physically interpreted. It is found that the wave-breaking phenomenon plays an important role in the nonlinear interactions between waves and that the second-order force components and the non-zero drifting forces are sensitively dependent on the depth of submergence, the spacing between twin cylinders and the cross-configuration of the cylinders.
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Wusheng SONG, Mitsuhisa IKEHATA, Kazuo SUZUKI
Article type: Article
Pages
25-36
Published: June 30, 1988
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A new approach to the slender body theory for a ship with forward velocity was presented by Maruo in 1982. This new slender ship theory (NSST) is based on an asymptotic expression of Kelvin-source around its track and quite different from other slender ship theories. The source density on the hull surface is determined by an integral equation of the Volterra type of the second kind instead of that of the Fredholm type of the Neumann-Kelvin problem. In the present paper, NSST is applied to the numerical solution for Wigley model. Distributions of source and pressure on the hull surface are solved by marching integration. Wave resistance is obtained by integrating pressure on the hull surface and the values agree well with measured ones. Then wave pattern of the model is calculated and the result is compared with measurement. On the other hand, since E function in the asymptotic expression of Kelvin-source is the complicated formula, it must take much operation time of an electronic computer to calculate E function precisely. A formula of fast numerical solution to E function is also presented in the paper.
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Yoji HIMENO, Hideaki NOUDO
Article type: Article
Pages
37-46
Published: June 30, 1988
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The present paper describes an analysis on the hydrodynamic effect of a fixed or oscillating wavy wall on the wall turbulence damping of the flow near the wall, and then on the velocity defect of the turbulent boundary layer of the plate. The turbulence damping is assumed to be represented by an eddy viscosity model proposed by Chapman and Kuhn. Then the model is applied to a wavy plate in which the boundary shape has a sinusoidal undulation, fixed in space or oscillating in time. The extention is made by assuming unsteady Oseen flow in the viscous sublayer of the turbulent boundary layer along the wavy wall. An analytical solution is obtained in terms of the geometrical parameters of the wavy wall, like height and wave length of the wall. The results show that the roughness function of the wavy wall, consequently the wall friction, becomes larger in most cases than that of a flat plate. However a little reduction of the friction is obtained in case when the amplitude of the wavy wall is small compared to the sublayer thickness and the ratio of the amplitude to the wave length is finite.
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Ichiro TANAKA, Hisayoshi TATANO, Ryozo HIRAKU
Article type: Article
Pages
47-55
Published: June 30, 1988
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The effects of freestream turbulence on the characteristics of a rudder with normal-wing-type section are investigated by wind tunnel experiments. Three models of different sizes of the rudder are used. Lift, drag and moment for three rudders are measured in the freestream of five different levels of turbulence artificially produced by turbulence lattices. The measurements are carried out in various wind speeds as well as various angles of attack of rudders. Large effect of turbulence on the forces of the rudder is demonstrated as the result of experiment.
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Hisaaki MAEDA, Akio KASAHARA
Article type: Article
Pages
57-63
Published: June 30, 1988
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We studied the 2-dimensional spectral measurment of short crested irregular water waves in order to understand characteristics of irregular water waves with directional spectra in ocean or model basin. The 2-dimensional spectral estimation depends on cross spectral estimation errors. In this paper, the 2-dimensional spectra estimated by Maximum Liklihood Method (M.L.M.) are discussed from the view point of cross spectral estimation errors. Those errors includs the white noise of a measured time-history and the errors of calibration factor or arrangement of wave probes. We found out that the 2-dimensional spectra estimated by M.L.M. depend strictly on the distance of arrangement of wave probes. According to numerical simulation, moreover, 2-dimensional spectra estimated by M.L.M. are affected directly by the errors of cross spectral estimation.
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Jun HUANG, Shieru NAITO
Article type: Article
Pages
65-72
Published: June 30, 1988
Released on J-STAGE: April 01, 2018
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Wavemakers are an important tool for ocean engigeering research. In experimental tanks at university and company, there are various wavemakers. Flap, piston and plunger types are more popular among them. Flap and piston type wavemaker thoery is well known, plunger type wavemaker is a little bit complicated mathematically. Such problems, as which type is the most efficient under certain water depth, or which type is the most suitable for large amplitude wave, have been a few studied. We studied on characteristics of flap, piston and plunger type wavemakers under same water depth with some assumptions. According to comparison of the maximum force needed to drive these wavemakers to make waves with same amplitude, the most efficient type could be found. On the other hand, by investigating the amplitude ratio of radiation wave to displacement of flap, piston and plunger, the most suitable type could be found for large amplitude wave. Furthermore we discussed the no-added mass wavemaker and the no-progressive wavemaker. It was known hat plunger type wavemaker are more efficient under deep water and flap type is the most efficient under shallow water. Piston type is more suitable to generate a large amplitude wave. No-added mass wavemaker and no-progressive wave wavemaker are interest types but it is difficult to make them realize.
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Shigeru NAITO, Kenichi KAKIZAKI, Akio YOKOTA, Shoichi NAKAMURA
Article type: Article
Pages
73-80
Published: June 30, 1988
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It is required to make ships renewable such as with high technology by taking modern techniques of electronic computors and controls, which is not at all inferior to airplane. When ships goes in harbor, captains becomes tense,when she goes in moderate ocean sea, he usually feels comfortable. It changes into rough sea condition, it is necessary for captains to operate her carefully. To avoid danger, his operating knowledges on ship performances and weather conditions is very important. His knowledges can be divided into three stages-recognition, judge and action process. Two intelligent systems are proposed as represented those processes. One is "Judge System of Dangerousness" based on results of seakeeping research, other is "Automatic Safety Navigation System" based on a production rule a kind of AI. To verify proposal systems, some simulation tests to avoid Typhoon moved across the ship route were carried out. In this report, results and discussions are presented.
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Omar KHATTAB
Article type: Article
Pages
81-90
Published: June 30, 1988
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The mathematical model of ship handling in confined waters has been extended to include the effect of two tractor-type tugs. This extended mathematical model was employed to investigate different towing arrangements of a 150,000 dwt tanker in shallow water at different wind speeds and directions in both full load and ballast conditions. Two towing arrangements were considered and a parametric study was carried out to calculate the maximum value of the towing vector diagram.
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Akinori YUMURO
Article type: Article
Pages
91-101
Published: June 30, 1988
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In order to provide basic data needed to predict harbour maneuvering motions, we carried out captive model tests in the wide range of drift angle and turning rate by employing a tanker-type ship. The tests conducted in the present study consist of CircularMotion Tests, tests using propeller-rudder system without the ship body, and propeller open tests. This report gives experimental results concerning characteristics of hydrodynamic forces acting on the ship hull, interaction effect between the propeller and the rudder, and open water characteristics of the propeller with large drift angle. As a result, it is clarified that flow-straightening effect of hull and propeller, and increase of rudder inflow velocity due to propeller working do not change remarkably with magnitude of the maneuvering motions. Furthermore, an attempt is made to predict thrust of the propeller having large drift angle by applying Glauert's hypothesis belonging to aerodynamics of a helicopter rotor with forward speed. The method mentioned above gives good agreement with the experimental results for the thrust of the propeller in free stream.
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Keiichi KARASUNO, Syunji JANUMA, Kunisaburo YONETA
Article type: Article
Pages
103-109
Published: June 30, 1988
Released on J-STAGE: April 01, 2018
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It is important to know the lateral added masses of ships which are either moving laterally to ward a quay or are moored near the quay, because the existence of the quay will alter that portion of potential flow component of the hydrodynamic lateral force which is caused by lateral acceleration. Furthermore, the other portion of this component, which is generated by lateral velocity, depends on the rate of change in the added mass. The remaining component in the force equation is viscous drag force which varies with velocity. Theoretical studies of the hydrodynamic lateral force operating in a restricted water area having a side wall have been conducted by Fujino [2,3] and Nonaka [4]. Experimental studies, however, have seldom been carried out, with the exception of Tsuji's research [5] which deals with lateral force at constant speed. This paper deals with model experiments of a 225GT fish carrier boat. These were carried out using lateral accelerating tests, and changes in the lateral added mass as affected by the quay were analysed. The equation of motion for the analysis is: m(dv)/(dt)=-m_y(s)(dv)/(dt)-(dm_y(s))/(dt)v-C_D・1/2・ρLd_m∣v∣v+Y_E, where s is the distance from the quay to the side wall of the ship. We drew the following conclusions: 1) the lateral added mass affected by the quay is from 2 to 4 times the added mass in open water, in accordance with the gap between the quay and the ship. This range corresponds to 0.1 to 0.0 times the ship breadth. 2) the cross flow drag cofficient C_D under conditions of accelerating motion is about 10% greater than under constant speed motion.
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Keiichi KARASUNO, Kunisaburo YONETA, Syunji JANUMA
Article type: Article
Pages
111-122
Published: June 30, 1988
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Moving at slow advance speed, a ship has a motion largely affected by any existing external forces and control forces. Then it moves with drifting angles which vary from small to large. Accordingly, when simulating ship maneuvering motions, the hydrodynamic lateral force Y" and the yaw-moment N' varying largely with ship's drifting angle, should be discribable by simple and accurate mathematical models covering all ranges of drift angle. For the purposes of developing the mathematical model, this paper adopts two important components of force : a linear lift force we call Y'_<uv>u'v', dominant within the range of small drift angles, and a cross flow drag force, C_<D90>m'_0v'^3, dominant within the rang of large drift angles, where C_<D90> is a cross flow drag coefficient of lateral ship motion and m'_i is an order i moment of the ship's profile area about midship. Futhermore, a nonlinear lift force, Y'_<uvvv>u'v'^3, is adopted for accurate description of the hydrodynamic force in the range of moderately large drift angles. We propose the following new mathematical model described within a wide range of drift angles: Y'=Y'_<uv>u'v'+Y'_<uvvv>u'v'^3+C_<D90>m'_0v'^3 N'=N'_<uv>u'v'+N'_<uvvv>u'v'^3+C_<D90>m'_1v'^3 In order to verify the models mentioned above, oblique tow tests were carried out using two fishing vesselr : one was a 1/21.5 scaled model of a 225 GT fish carrier boat at with one load condition and the other a 1/6.5 scaled model of a 6.5GT coastal small fishing boat at with nine load conditions. According to this analysis, these mathematical models have been found to fit closely experimental values of hydrodynamic lateral force and yaw moment.
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Norimasa TAKAGI, Yoshihiro SUENAGA, Masaaki SAKUTA
Article type: Article
Pages
123-131
Published: June 30, 1988
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Many wave energy absorption system currently proposed can absorb wave energy with fairly high efficiency, regarding wave energy at a specified frequency band ; but they are said to lower their absorption efficiency in irregular waves, This is due to the fact that while waves themselves are composed of wide-range frequencies, the natural frequency of the wave energy absorption system itself is basically a single one, and is so arranged that the wave energy absorption efficiency will become the greatest in the vicinity of its natural frequency. To overcome this discrepancy, ingenuity has been used to estimate the incident waves and functionally change the natural frequency, but this method has not yet been able to enhance the efficiency. The present study has conceived that the wave energy absorption system is made to correspond to wide frequency bands, which the irregular wave has, by providing a plural number of natural frequencies in a single system, not by changing the natural frequency of the system itself. An attempt has been made to grasp experimentally the wave energy absorption characteristics. In the present system, it was impossible to provide a plural number of natural frequencies in a single unit, owing to the restr ction in scale. The authors solved this problrem by paying attention to the fact that the water column in the U-shaped tube had a natural frequency, and the length of this water column, not its volume, can determine the natural frequency. This paper verifies the validity of determing the natural frequency in the oscillating water-column-type wave energy absorption system, using the same concept as that of the water column in the U-shaped tube, and reports the absorption characteristics when a plural number of water columns, which have different natural frequencies, is used in a single system to absorb wave energy.
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Yoshikazu MATSUURA, Kimio SAITO, Kenji ARIMA, Shigehiro HAYASHI
Article type: Article
Pages
133-143
Published: June 30, 1988
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In this paper, the effect of shallow water on the two-dimensional added mass coefficient C_v and the three-dimensional correction factor J_v for the vertical hull vibration of the ships are investigateg. For this purpose, the numerical calculations using the singularity distribution method as well as the model experiments for the mathematical models have been carried out by changing the water depth. From this study, it is shown that the comparison between the results of the calculations and the model experiments gives a fairly good agreement. And it is also found that the shallow water has a considerable effect on the two-dimensional added mass coefficient C_v, while it has a negligibly small effect on the three-dimensional correction factor J_v. In the last part of this paper, the two-dimensional added mass coefficient C_v obtained from the numerical calculations for the vertical vibration of the body with the various sectional shapes are presented in the chart form and it will be used for an easy estimation of the added mass in the shallow water at the initial design stage of the ships.
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Masaaki HASHII, Yoshihito SAKAKIBARA
Article type: Article
Pages
145-151
Published: June 30, 1988
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Diesel-electric propulsion ship has attracted notice recently because the "QE2" was successfully modificated from steam-turbine. Diesel-electric propulsion has demerits such as heavier weight, more initial cost and fuel in comparison with diesel-geared. However diesel-electric propulsion is capable of wide ranged operation power, supplying both of propulsion and hotel survice power with one "power station", easy vibration isolation and the greatest reliability because of redundancy. In this article, we estimate availability of majority decision stand-by redundancy system on diesel-electric propulsion ship assuming stopped generators sets by troubles are not restored during a voyage. We could realise a ship of which diesel-electric propulsion system constructed by multi-generators sets were possible to supply normal power (85% of maximum power) for 30 days with availability more than 95% without restoration, if failure rate of a generator set were not more than 2×10^<-4> (event/hour). Of course, there are causes of machinery troubles on ship, such as low quality heavy fuel oil, that differ from contingent origins we consider in this paper.
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[in Japanese]
Article type: Article
Pages
153-156
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
157-160
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
161-164
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
165-167
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
169-
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
171-172
Published: June 30, 1988
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[in Japanese]
Article type: Article
Pages
173-174
Published: June 30, 1988
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Article type: Appendix
Pages
175-179
Published: June 30, 1988
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Article type: Appendix
Pages
App2-
Published: June 30, 1988
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Article type: Appendix
Pages
App3-
Published: June 30, 1988
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Article type: Appendix
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Published: June 30, 1988
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Article type: Appendix
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Published: June 30, 1988
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Article type: Appendix
Pages
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Published: June 30, 1988
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Article type: Appendix
Pages
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Published: June 30, 1988
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Article type: Cover
Pages
Cover2-
Published: June 30, 1988
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Article type: Cover
Pages
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Published: June 30, 1988
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