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Article type: Cover
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Published: March 30, 1974
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Article type: Cover
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Published: March 30, 1974
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Article type: Appendix
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Published: March 30, 1974
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Article type: Index
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1-
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
1-2
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
3-7
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
8-18
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
19-28
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
29-37
Published: March 30, 1974
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[in Japanese]
Article type: Article
Pages
38-42
Published: March 30, 1974
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Takaaki ISHIHAMA, Shin TAKEUCHI
Article type: Article
Pages
43-49
Published: March 30, 1974
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It is due consideration for ship designer to predict the natural frequency of funnel to avoid the resonance with hull in the preliminery design stage. The natural frequency of funnel depends on the weight distribution of its body and the rigidity of the foundation on which it is positioned. In this report, the funnel body is idealized as a cantilever beam whose end is elastically supported. The weight distribution is replaced by lumped for feasible analysis. On the other hand, the structure of the foundation is assumed to be of plane grillage which consists of primary supporting members under deck. Furthermore, the correlation between fore and aft and athwartship vibration is taken into account. Based on the above assumption, a computer program is devoloped to calculate the natural frequency of funnel as well as the correlation between the regidity of the foundation and the natural frequecy. By comparing the calculated value with the measured one, the present method is proved to be fully practical, and, also, a simple formula to predict the natural frequency of funnel is proposed.
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Shoichi SUDO, Motomu TOYA, Tsutomu KIMURA, Takashi JONO, Koichi YOKOO, ...
Article type: Article
Pages
51-60
Published: March 30, 1974
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This paper describes the results of full scale speed trials as well as model experiments, with the propeller under various load conditions. These experiments were conducted with the intention of examining the model-ship correlations of self-propulsion factors, especially thrust deduction fraction. When the model-ship correlation in ship propulsion are considered, correlations of hull resistance and thrust deduction fraction cannot be directly examined because of the difficulty of ship resistance measurement. The authors tried to examine the behavior of thrust deduction fraction of full scale ships without measuring hull resistance, by means of varying the propeller load. Two sister ships were used for the experiments: 163,000 DWT type ore-oil carriers built at Innoshima Shipyard of Hitachi Shipbuilding & Engineering Co. Ltd. In addition to the ordinary speed trials, special trials were carried out with the ships towing sea-anchors on both sides. The sea-anchors gave additional resistance to the ships, and were very useful for varying the propeller load. A model of 9 m in L_<pp> was tested in Ship Research Institute, the Ministry of Transport. Self-propulsion tests of the model were conducted with various skin friction correction, corresponding to the conditions of the ship speed trials with sea-anchors. Comparing the results of the ship speed trials with those of the model experiments, the model-ship correlations of self-propulsion factors were examined in particular ways. Conclusions obtained are as follows, though further investigations may be necessary to be precise. (1) Results of the experiments differ from the general knowledge until now; the values of the self-propulsion factors, excepting (1-t) in the full load conditions, vary with the propeller load. (2) η_R rises with the increase of the drag (additional resistance to the ship). The η_R values of the ship seem to be the same as those of the model. (3) When the drag is increased at a constant speed, (1-w) increases in the full load condition while it decreases in the ballast condition. (4) Concerning (1-t), it seems that: a) In the full load condition, the vaiues of (1-t) remain constant regardless of the variation of the propeller load as usually believed. b) In the ballast condition, the values of (1-t) vary most irregularly in the self-propulsion factors, but have a general tendency that they decrease with the increase of the propeller load coefficient.
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Noboru KAWAGUCHI, Katsuyoshi TAKEKUMA, Kiyoshi HASHIGUCHI, Tatsuji ISE ...
Article type: Article
Pages
61-68
Published: March 30, 1974
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It is increasingly important for ship owners and ship builders to study the ship service performance under seaway in order to check their design considerations and to make the economic evaluations precisely for their ships. For this purpose, the analysis of the ship service performance should be performed on such standardized method that is suitable to compare the analyzed results with each other and is able to apply them to the new ships under design. The authors developed a new analyzing system of the ship service performance which matches the above demands sufficiently. In this system, the fouling and the aging effects are obtained in the form of increment of correlation factors, i.e., the increment on roughness effect δΔC_f and that on wake fraction δe_i, from the abstracted log book data, and other elements which affect ship's performance under seaway, for examples, wave and current effects, are also obtained analytically. Furthermore, the evaluation of the service performance on a given ship becomes possible by the use of above correlation data. The computer program for the system has been completed. As an example, the service performances of a cargo liner and a bulk carrier are analyzed by the use of this newly developed system.
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Fukuzo TASAI
Article type: Article
Pages
69-78
Published: March 30, 1974
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A calculation method of the transmitted wave height and the reflected wave height by the oscillating cylinder moored in regular beam waves are developed first. Secondly, the theorctical calculation results of transmitted wave height, not only for restrained condition but also for oscillating condition, are compared with model experiments. Thirdly, according to Maruo's theory, the drifting forces acting on the circular cylinder heaving in beam waves are calculated by using the theoretical reflection coefficient obtained by this study and compared with Maruo's computation results. Conclusions of the present study are summarized as follows: 1) Calculated theoretical results of transmission coefficients are in good agreement with model experimental ones. 2) At the resonant frequency of oscillation, the value of transmission coefficient and reflection coefficient is respectively equal to the reflection coefficient and transmission coefficient for restrained condition. 3) Drifting forces calculated by Maruo's theory and the exact values of reflection coefficient show a different tendency from the Maruo's computation results, and the value of drifting force at the resonance condition does not show maximum value such as Suehiro's experimental results. Accordingly, it results that Maruo's theory for drifting force can not explain the experimental results.
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Yoshifumi TAKAISHI, Taihei YOSHINO
Article type: Article
Pages
79-91
Published: March 30, 1974
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Since container ships have large deck openings on their slender hulls, it is very important to estimate the wave loads, or torsional and bending moment, as accurately as possible for designing such a vessel. Though some experimental as well as theoretical investigations with regard to this problem have recently been carried out, the comparison between the theory and the experiment seem still insufficient to apply the theory to the practical use, except the vertical bending moment. In this paper the authors investigate the vertical and lateral bending moment as well as the torsional moment acting on the midship section of a container ship, using the results obtained by the model tests and the theoretical calculations based on the so called strip method, which cover wide range of wave conditions and ship speed in oblique regular waves. The results show that the theory agrees rather well with experiment for vertical and lateral bending moments, while discrepancy is remarkable for the torsional moment in quartering seas. The steady deviation of the vertical bending moment in still water and in waves and the combined bending moment induced by the vertical and lateral bending are also described with the experimental data.
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Masahiro MATSUI, Masanori SUGIURA
Article type: Article
Pages
93-100
Published: March 30, 1974
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In this paper authors focused attention on a dynamic positioning system of n-footings type semi-submersible platform using a mathematical model which is very simple but can simulate well an actual model experiment. The mathematical model is based on following assumptions. 1) Our platform is a pancake shape n-footings type with a thruster installed under each footing. 2) Hydrodynamic forces of submersible bodies except for drags are negligible. 3) Forces acting on each footing are homogenious in direction and can be superposed. Strictly speaking the model must be shown by nonlinear equations. But closed form mathematical expressions for the optimal control equation in nonlinear problem cannot be obtained analytically except in very special case. Therefore a linear approximate equation was introduced. For this linear equation, it is not difficult to research optimal control gains. From the optimal control theory, it is well known that the solution minimizing a quadratic form performance measure is a feed back control system. In the present paper, some numerical calculations on the motion of platform which was tried to keep the position by P.I.D feed back control were carried out and compared with the results of model experiments. And it was found that the theoretical results agree with experimental values.
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Article type: Appendix
Pages
101-104
Published: March 30, 1974
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Article type: Cover
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Published: March 30, 1974
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