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Article type: Cover
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Published: March 30, 1979
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Article type: Cover
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Article type: Appendix
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App1-
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Article type: Appendix
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App2-
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Article type: Appendix
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Nobuyoshi MUROI, Ryuji SAKATA, Yoshio YAMAGAMI
Article type: Article
Pages
1-8
Published: March 30, 1979
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This report relates to the analysis of measurement data with periodicity, such as those of model tests carried out to investigate the oscillating characteristics of vessels and offshore structures in regular wave. The most important problem in this analysis is how to estimate a signal of periodic wave components from the short data disturbed by noise having an unknown basical wave period ; that is, it depends on how to search for the unknown wave period. The authors have approached a solution of this difficult problem by using an index "G_p" described in the following text, which is like a projection ratio of Fourier coefficient powers. This method has been developed in answer to practical demands and used with satisfactory results so far.
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Hiroshi OKAMOTO, Yoshio YAMAGAMI, Ryuji SAKATA
Article type: Article
Pages
9-16
Published: March 30, 1979
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It seems that a standard calculation method of motions of box type vessels testified by experimental data has not been definitely established yet. Therefore, as a means to estimate the hydrodynamical forces acting on the box type vessels and their motions, the authors have manufactured a forced oscillator and carried out a forced oscillation test and wave induced force test so as to obtain various coefficients for the equations of the motions and wave induced forces. This paper presents the forced oscillator and a part of the results of the tests conducted. The results of the tests have been arranged to correspond to those of the theoretical calculations by two-dimensional source distribution method, by which it has been found that the test results and the theoretical calculation results mostly agree with each other except the damping moment coefficient of roll. However, in such box type vessels as having a large B/d and a large shallow water effect, differences have been found between both results. Thus, it has been made clear that the test method using the forced oscillator is a good means to solve the problems of shallow water effect, three-dimensional problem, etc. which the box type vessels have and also useful and helpful for improvement of the accuracy of the theoretical calculation.
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Akira MASUMOTO
Article type: Article
Pages
17-31
Published: March 30, 1979
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A second-order potential solution for a two dimensional symmetric cylinder in regular waves is sought by regular perturbation theory. In the development of this theory, the assumptions are as follows. (1) A perturbation parameter is taken as the steepness of incident waves of which length is the same order of the beam of the cylinder. (2) The section of the cylinder is Lewis form. (3) The mean position of the cylinder is immovable-that is, the external force with the same magnitude and the opposite direction of drifting force acts on the cylinder. In the resulting potential theory problem, the first-order potential, the second-order radiation potential, and the second-order potential due to body surface interference are solved by Ursell-Tasai's method, and the second-order potential due to free surface interference is solved by Lee's method in consideration of global mass conservation principle. Numerical computations are made for the cases as follows, the circular and rectangular cylinders undergo forced sinusoidal motion in heave, those cylinders in regular waves, and rectangular cylinder floating in regular waves. The results are presented in graphs. Some of the results summarized as follows : (1) The calculation results of the second-order hydrodynamic forces for heaving circular cylinder show good agreement with experimental results by Tasai and Koterayama. (2) The culculation results of drifting force by pressure integral are in agreement with ones by momentum theory. (3) The sinking force and the heel moment of a floating body in regular waves become extremely large at rolling natural period.
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Masashiro KOYANAGI, Sumihiro EGUCHI, Hiroshi TERAO, Mamoru UCHIDA, Sei ...
Article type: Article
Pages
33-42
Published: March 30, 1979
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The impact pressure which occured upon the bottom of a high speed hard chine deep V form small craft (YAMAHA STR-20HT) running in rough seas was measured. The vertical acceleration at bow and stern and the motion (pitching and rolling) of the craft were also measured. The full scale experiment was carried out at Imagire just out of the Lake Hamana, that is, the sea of Enshu between 1975 and 1977 by the Japan Craft Inspection Organization. Concluding remarks of this experiment are as follows, (1) Large impact pressures and accelerations were observed in condition of ahead and oblique seas. (2) The porpoising occured in heavy sea, and the maximum pressure (5kg/cm^2) was recorded at the stern of the craft. (3) Smaller the dead rise angle of the surface where the pressure gage is installed becomes larger the impact pressure gets. And these values belong to log-normal distribution as statistical characteristics. (4) The maximum expected impact pressure which acts upon a high speed small craft within its life seems to be a function of dead rise angle of the surface where the pressure gage has been attached.
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Omar M. M. KHATTAB, Kensaku NOMOTO, Yusuke HORIUCHI
Article type: Article
Pages
43-50
Published: March 30, 1979
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In the previous report [1], the transfer function approach to the ship manoeuvring in canals was introduced with particular reference to course stability and automatic steering. Also a simple mathematical model of ship behaviour was presented. In this report we introduce a real time ship handling simulator to study the behaviour of a ship in canals, taking account of the human operators incorporated. The ship handling simulator is a very useful tool to examine the behaviour and training of the ship operators and also provide technical information on the design and the development of the waterways. We studied the learning process of the new ship handlers as well as the human ability to control ships in canals under difficult conditions. At the same time the ship handling simulator is used in place of a full scale ship to carry out Zig-zag manoeuvre from which we can estimate the parameters of the simplified mathematical model of any given ship. We find that, the effect of learning the skill is remarkable and the training could be done firstly on the simulator. The personal differences is very small once one get the skill. In order to get the skill, sound understanding and continuous training are necessary. The simplified mathematical model parameters of a given ship in a canal can be determined by carrying out Zig-zag manoeuvre of small amplitude, say 5°/1.5° Zig-zag test.
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Shigeru NAITO, Shoichi NAKAMURA
Article type: Article
Pages
51-63
Published: March 30, 1979
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In order to investigate the propeller characteristics at racing condition in waves, open water tests with a five bladed 15cm diameter propeller are carried out as to the following conditions. (1) In still water varying propeller immersion. (2) At the condition of forced heave oscillation in still water with two kind of propeller immersion. (3) In regular waves of different wave height with a shallow propeller immersion. (4) In irregular waves varying propeller immersion The effect of propeller immersion on the open water characteristics is studied, and the propeller load fluctuations at the experiments of (2)∼(4) are measured. It is shown that the propeller load fluctuations at racing condition in waves have two components, one is due to the orbital velocity of waves and the other is caused by the variation of propeller immersion, and that the smaller the immersion, the larger the latter component becomes. To analyse the nonlinear random phenomenon of propeller load fluctuations at racing condition in irregular waves, a mathematical model showing the relation between the propeller load and immersion is introduced and the analytical equation is derived for obtaining the spectrum of that phenomenon.
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Yeun-Junn LIN, Takao INUI, Hisashi KAJITANI, Yoshihiro TSUCHIYA, Makot ...
Article type: Article
Pages
65-74
Published: March 30, 1979
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An improvement of hull forms with less wave resistance is presented using Guilloton's transformation. The equivalent source distribution for a given conventional ship form is obtained in a mathematical flow field where the linear thin ship theory becomes applicable. Adding a small amount of source distribution, the optimization is carried out. The optimized total source is re-transformed to the real hull, that is, the modification of the given hull. The method is applied to the fore-body of a refined container ship and a very slightly modified hull is obtained. Two models, "the given hull" and "the modified hull by the present method" are resistance-tested and wave-analyzed. Results indicate that ; 1) the present method is efficient for improving conventional hull forms, and 2) the effectiveness of Guilloton's transformation is attributed mainly to the improvement of the linear free surface condition.
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Hajime KAWAKAMI, Tokio OHNISHI
Article type: Article
Pages
75-83
Published: March 30, 1979
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There are three kinds of numerical integrations to solve the equation of motion for systems with a large number of freedom ; Solutions by the finite difference method, the Pade approximation and the finite element method. So far, various methods based on the finite element method have been examined. Two years ago, the authors proposed a new algorithm based on the finite element method and showed its usefulness. In this paper, first, the accuracy of the authors' algorithm is studied mathematically and compared with other algorithms. Then, in order to confirm the above-mentioned results, the numerical calculation of responses of the linear system with a single degree of freedom is carried out. The features of the authors' algorithm are summarized as follows : 1) The algorithm derived from 2-nodes element is equivalent to the one of β method for β=1/6 2) In the case of 3-nodes element, the algorithm is as accurate as the one of the Argyris method. 3) The algorithm derived from 4-nodes element has very high accuracy and takes less time in computation than other algorithms.
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Noboru AWAZU, Jiro SEGAWA, Mikihiro KOBAYASHI, Yoichi OMURA
Article type: Article
Pages
85-93
Published: March 30, 1979
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Heavy derricker "ATLAS MARU" was delivered to Mitsui O.S.K. Line, Ltd. on March 20th, 1978 by Kobe Shipyard & Engine works of Mitsbishi Heavy Industry, Ltd. employing the authors. The heavy derrick on ATLAS MARU is a Kawasaki guyless omnirange rotary type with 600ton lifting capacity. This capacity is the largest of heavy derrickers in the world. But, because of the limitation of space design, the depth of the tower mast of the heavy derrick under the upper deck was obliged to be smaller than that of the 450ton heavy derrick which had the largest lifting capacity of the same type heavy derricks. Authors carried out the strength analysis by FEM and stress measurements on the base structure of the heavy derrick. Because of good correspondence between both results, it was confirmed that the winch platform contributes to support the heavy derrick, and the simplified method to calculate the strength of the base structure was considered. There was fairly good correspondence between measuremonts and results of simplified method. Accordingly, this method will be available to estimate the scantlings of the base structure of heavy derrick which depend on planning depth of the tower mast under the upper deck.
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Toshiyasu TSUNENARI, Hideo ONO
Article type: Article
Pages
95-101
Published: March 30, 1979
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A simplified crack propagation model which takes into consideration the retardation effect was proposed in last report. It was confirmed that this model simulates the crack propagation behavior of SM58Q steel under quasi-random load very well. In the present report, the applicability of this model to Al 2024-T351 alloy was investigated to examine the possibility of application of this model to various kinds of materials. The conclusions obtained mainly were as follows ; (1) This model holds good to Al 2024-T351 alloy as to SM58Q steel, and range of applicability of this model to various kinds of material was increased. (2) The crack retardation effect in Al 2024-T351 alloy is greater than that in SM58Q steel. (3) In the quasi-random loading test, the smaller the load cycles in 1 block (ΔN) or the smaller the correlation factor (ρ) of random number, the greater the retardation effect becomes.
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Article type: Index
Pages
103-
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
105-112
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
113-119
Published: March 30, 1979
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[in Japanese], [in Japanese]
Article type: Article
Pages
121-128
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
129-133
Published: March 30, 1979
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[in Japanese], [in Japanese]
Article type: Article
Pages
135-
Published: March 30, 1979
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[in Japanese], [in Japanese], [in Japanese], [in Japanese]
Article type: Article
Pages
136-
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
136-138
Published: March 30, 1979
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[in Japanese], [in Japanese]
Article type: Article
Pages
138-139
Published: March 30, 1979
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[in Japanese], [in Japanese]
Article type: Article
Pages
140-141
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[in Japanese]
Article type: Article
Pages
141-142
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[in Japanese]
Article type: Article
Pages
142-144
Published: March 30, 1979
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[in Japanese], [in Japanese]
Article type: Article
Pages
144-146
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
146-147
Published: March 30, 1979
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[in Japanese]
Article type: Article
Pages
147-
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[in Japanese], [in Japanese]
Article type: Article
Pages
149-156
Published: March 30, 1979
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Article type: Appendix
Pages
157-158
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Article type: Appendix
Pages
159-164
Published: March 30, 1979
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Article type: Appendix
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App7-
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Article type: Cover
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Article type: Cover
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