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Article type: Cover
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Cover1-
Published: June 30, 1985
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Article type: Index
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Toc1-
Published: June 30, 1985
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Article type: Appendix
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Published: June 30, 1985
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Katashi TAGUCHI, Mitsuo KISHI, Yoshinori MINAMI
Article type: Article
Pages
1-10
Published: June 30, 1985
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The cognitive map technique, a heuristic computer aided method for structural modelling based on graph theory, is employed to build systematically up a structural model of social and/or economic system. In this study, an algorithm to prepare cognitive maps containing loops is proposed. Whether the prepared cognitive map is propriety is judged by using the conditions of (1) There should not be any illogical imbalances in the map and (2) The system model described by the cognitive map is to be stable to some extent. For the second condition, analysis on system dynamics is carried out using the concept of pulse process which is formulated with state equation of discrete-time system. Another simulation study using KSIM is also carried out on the vital concepts extracted from the revised cognitive map. The proposed method is applied to the preparation of the cognitive map for maritime industry, which is composed of shipping, shipbuilding, and port & harbour, under recession in the developed countries. The structural issues involved in the maritime industry are examined, and the influence of innovation of the related production technology is simulated.
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Toshiro SAEKI, Tadao TAKAI, Akihisa KOKUMAI
Article type: Article
Pages
11-19
Published: June 30, 1985
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This paper describes a simulation study on the noise adaptive autopilot (NADCON) for some ships with various degrees of dynamic course stability. NADCON optimizes control gain to minimize an energy loss and has the adaptive estimation function of the external disturbances. A number of course-keeping simulation under the various environmental conditions were carried out for evaluating the performance of NADCON. The results were obtained as follows: (1) NADCON has a good course stability performance for course unstable ships as well as stable ships. (2) NADCON has a high adaptability to various change of sea state and ship speed. (3) NADCON has an advantage of the energy saving performance compared with a PID type autopilot.
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Masashi KASHIWAGI
Article type: Article
Pages
21-30
Published: June 30, 1985
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This paper describes a new slender-body theory for the sway and yaw motions of ships, moving with forward velocity in calm water. In analyses for vertical plane motions of heave and pitch by use of the Slender-body theory, the unified theory established by Newman and Sclavounos is known as a powerful method. The present study is an extension of this unified theory to the lateral motions of ships. The unified theory emphasizes that it is reasonable to include an expression for three-dimensional interaction effects in the so-called strip theory, although the strip theory for lateral motions has been considered so far to be valid for all frequencies of practical interest. Computations are also made for the added-mass and damping coefficients and then results are compared with experiments for a container ship model in order to investigate the relative importance of three-dimensional effects on the hydrodynamic sway force and yaw moment. As a result of comparison, it is revealed that three-dimensional effects are not so significant and that another formulation, independent of the usual strip-theory concept, must be considered in order to incorporate the forward-speed effect in the inner problem of slender-body theory, particularly for relatively high Froude numbers.
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Ken TAKAGI, Shigeru NAITO, Shoichi NAKAMURA
Article type: Article
Pages
31-38
Published: June 30, 1985
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A numerical method, so-called Boundary Element Method (BEM), for simulation of two-dimensional nonlinear wave problems is described. The method is based on potential theory, and it is assumed that the boundary conditions are fully non-linear in inner domain but linear potential is used in outer domain and the problem is treated as a transient problem. We performed computations of the following three problems. (1) Wave breaking problem of large amplitude transient wave. (2) Diffraction problem in large amplitude transient wave. (3) Radiation problem of surface piercing body. Computed results are in good agreement with experimental results and show the nonlinear characteristics.
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Shigeru NAITO, Shoichi NAKAMURA, Akira NISHIGUCHI
Article type: Article
Pages
39-45
Published: June 30, 1985
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It is well known that the calculated added resistance of ship forms with blunt bow in short length waves by the assumption of slender body is considerably small compared with the measured results. In this report, the reasons of difference are discussed. To study the propagation of elementary waves in the flow field around the hull form, which is deformed by the existence of blunt bow ship, numerical calculations are performed by using the ray theory. It is found that some rays of incident waves propagate to the far field, but some rays cannot reach the far field and break by the interaction between the basic flow and the wave field. Added resistance in waves is obtained by integrating the pressure directly over the hull surface and is compared with the measured results. As the results, the reason of difference is fairly clarified and it is shown that the component of wave breaking can be estimated by using the ray theory.
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Norimasa TAKAGI, Koichi MASUDA, Masaaki SAKUTA
Article type: Article
Pages
47-54
Published: June 30, 1985
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Using the results of numerous studies made on cylindrical columns and angular columns -- the major constituent members of semisubmersible structures -- a method of predicting the vortex making damping force on the overall structure is proposed, and the suitability of this prediction method is studied by comparing the predicted results with the experimental results. In addition, the results of this method were compared with the experimental methods in the treatment of the joints of members, the effects of mutual interference between the joints, and three-dimensional correction. thus a practical method has been proposed.
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Masaaki NAMIMATSU, Seikoo OGIWARA, Hiraku TANAKA, Munehiko HINATSU, Hi ...
Article type: Article
Pages
55-64
Published: June 30, 1985
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The present paper descridescribes the experimental study on hull surface pressure making use of three Wigley geosim models relating to the 17th ITTC cooperative works. The results of experiments are applied to some investigations of the characteristics of pressure resistance and resistance components, Main conclusions of the investigations are as follows ; (1) A certain Reynolds number effect is recognized in pressure distribution near the stern. (2) The pressure resistance obtained by integrating the measured local pressure over the hull is compared with residual resistance, wave resistance and wave pattern resistance. Further, the frictional resistance derived by subtracting measured pressure resistance from total resistance is evaluated by comparing with the skin friction formulae of flat plate. (3) The pressure resistance components for forebody and afterbody are respectively analyzed. The contribution of pressures to resistance above load water line is predominant at forebody, while the substance of the hump/hollow of wave resistance are exemplified in the pressure resistance of afterbody. (4) The measured pressure distributions are compared with the calculated results by modified Guilloton's method which includes the boundary layer effect on wave source potential, and good agreements are obtained.
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Seikoo OGIWARA, Masaaki NAMIMATSU, Hiraku TANAKA, Munehiko HINATSU, Hi ...
Article type: Article
Pages
65-75
Published: June 30, 1985
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This paper describes some experimental results on sinkage and trim for Wigley geosim models in the 17th ITTC cooperative works and discusses the analytical prediction by means of duoble model flow assumption, linearized wave resistance theory and boundary layer theory. Futher the sinkage of model is evaluated by using pressure measurements on the hull surface. The results of investigations are obtained as follows; (1) Scale effect is not recognized in measured values of sinkage and trim in towing condition for geosim models, and the scattering of measured date of sinkage is considered to be the effect of seiche in the tank. (2) Sinkage at low speeds is roughly estimated on the assumption of double model flow, however, sinkage and trim are influenced by free waves as Froude number is increased and behavior of sinkage and rim is closely related to wave making resistance. (3) From the evaluation of sinkage by using the pressure measurements on the hull surface, it is found that the sinkage is predominently caused by the pressure depression around the hull. Viscous effect on sinkage and trim is discussed through the boundary layer theory, however the viscous effect is very small.
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Nobuo NAGAMATSU, Hodaka SHIMIZU
Article type: Article
Pages
77-85
Published: June 30, 1985
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Recently, many studies on propeller slipstream have been carried out. It is very important to investigate slipstream of propeller, not only for analysis of propeller performance, but also for design of enegy saving devices around the propeller. In this paper, first, the induced flow fields around conventional propeller (CP) and high skew propeller (HSP) were investigated by experiment. The velocities were measured by 5-hole pitot tube and flow visualization was carried out. Secondly, induced velocities were calculated by use of vortex wake model based on experimental data, In that calculation we made use of circulation distribution of each b1ade which derived from other propeller lifting surface program. The good agreement was obtained between calculated values and measured values.
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Ryoichi KAJIMA, Yasuyuki TODA, Toshio SUZUKI
Article type: Article
Pages
87-95
Published: June 30, 1985
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Recently many people investigated the velocity distribution around the ship stern and found the very complicated shapes of equi-velocity contours and longitudinal vorticity component. They guess that 3-d separation and the roll-up of vortex layer occur near the stern in combination with the flow visualization. The theoretical investigation is also made but sometimes calculation was diverged away in most part of the stern flow field. In this paper, (1) the velocity distribution is investigated experimentaly by use of a small 5-hole pitot tube in detail, and (2) based on its result, we propose a theoretical method to predict the velocity distribution around the ships tern. Numerical calculation is made along the local streaming flow direction and the velocity defect components are calculated simultaneously. The calculation is continued step by step under the assumptions that the fluid is inviscid but rotational Obtained results show similar tendencies with experimental results.
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Yasuyuki TODA, Ichiro TANAKA, Hiroshi SUGIOKA, Yasuhito OTUKA
Article type: Article
Pages
97-106
Published: June 30, 1985
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An integral method of three-dimensional boundary layer with higher order terms is discussed. The pressure and metric coefficients variation across the boundary layer due to the effect of surface curvature is taken into account. The momentum integral equations obtained by use of Lame's equations take the form easy for physical understanding. The numerical calculation is made with small cross flow assumption around two simple models. Calculated results explain the results of experiments fairly well.
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Hajimu MANO, Hiroshi KAWABE
Article type: Article
Pages
107-116
Published: June 30, 1985
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The stress concentration problem around a discontinuity in a hull given member is studied. As the first step, authors studied on the problem around a hole in an infinite elastic plate under the uniform loading. Authors bring the focus into finding out the optimum configuration which have minimum stress concentration factor among the holes having a given aspect ratio and being formed with fair curve, and lower limit value of the stress concentration factor. The configurations are chosen from those which are expressed by the mathematical descriptions, namely, the higher order ellipses and the modified ellipses. As the result of investigation, it has been shown that the optimum configuration is more similar to the rectangular rather than to the ellipse, which is usually considered as the one of the optimum configurations. The value of stress concentration factor is about 15% to 25% smaller than the ellipses. Studying the characteristic of tangential stress distribution around the hole edge, authors concluded that the distribution of the hole of the optimum configuration would be uniform. The distribution of the above result is approximatelyuniform, so these are approximately optimum configuration for the given aspect ratios. Authors proposed the inverse procedure to find a configuration with more uniform stress distribution from an initial one as the above approximate optimum configuration. Applying the procedure and investigating the result, authors concluded the above configuration is to be regarded practical optimum configuration and the value of the stress concentration factor is also the lower limit under the loading condition.
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Yoshikazu MATSUURA, Kouhei MATSUMOTO, Mitsuru MIZUUCHI, Kenji ARIMA, H ...
Article type: Article
Pages
117-126
Published: June 30, 1985
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Many kinds of machinery, steel structure, vehicle and others have been freed from harmful and troublesome vibration with dynamic damper since the theory of the dynamic damper was established by Den Hartog at the early 1900's. This paper deals with the mechanical damper for reducing ship vibration. The authors devised three kinds of dynamic damper type here, namely beam spring type, rubber spring type and multi-beam spring type. The damper effect of these dynamic dampers were studied experimentally and theoretically. The authors obtained the following conclusion from this study. (1) The damper is the most effective when its natural frequency harmonizes with the ship's one, and larger is the weight ratio of dynamic damper to ship, more effective the damper is. (2) The large damping factor of dynamic damper installed on ship has effect to reduce the displacement amplitude of ship at resonance (3) The dynamic damper should be installed at the loop of mode shape, and the installation of the damper on the node is confirmed experimentally to be ineffective. (4) The ship model with two dampers has the three coupled natural frequencies, and the mode shape of ship at both the highest and lowest natural frequencies is two noded mode and the other is one noded mode. (5) The multi-beam spring type damper is found experimentally to behave as one damper on condition that its own many natural frequencies scatter in less than 5%. (6) The authors applied not only the coventional mass spring model but also the beam model with mass spring as calculation model, and they showed good agreement between measured and calculated frequencies of the ship model with the dynamic dampers.
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[in Japanese]
Article type: Article
Pages
127-139
Published: June 30, 1985
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[in Japanese]
Article type: Article
Pages
141-144
Published: June 30, 1985
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[in Japanese], [in Japanese]
Article type: Article
Pages
145-147
Published: June 30, 1985
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Article type: Appendix
Pages
149-152
Published: June 30, 1985
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Article type: Appendix
Pages
App2-
Published: June 30, 1985
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Article type: Appendix
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App3-
Published: June 30, 1985
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Article type: Appendix
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App4-
Published: June 30, 1985
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Article type: Appendix
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Article type: Appendix
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App6-
Published: June 30, 1985
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Article type: Appendix
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App7-
Published: June 30, 1985
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Article type: Appendix
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App8-
Published: June 30, 1985
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Article type: Appendix
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App9-
Published: June 30, 1985
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Article type: Appendix
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App10-
Published: June 30, 1985
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Article type: Cover
Pages
Cover2-
Published: June 30, 1985
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Article type: Cover
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Published: June 30, 1985
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