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Article type: Cover
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Published: June 30, 1983
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Article type: Index
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Published: June 30, 1983
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Article type: Appendix
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Published: June 30, 1983
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Masaru MOKUNAKA, Chiaki KISHIDA, Nobuo MURAKAMI
Article type: Article
Pages
1-9
Published: June 30, 1983
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At the time when the primary semisubmersible platforms were exploited, principal dimensions of a semisubmersible were determined by only fulfilling the requirements given to it, which means no optimization was made. Since 1970s, several attempts have been made to design optimum semisubmersible platform, but they were aimed only at optimizing motion characteristics and cannot be regarded as researches into the actual optimum semisubmersible. This paper presents an optimum designing method which aims not only at optimum motion characteristics but also optimum stability and economic efficiency. This method determines the most economical principal dimensions of a semisubmersible drilling rig which satisfy the requirements for motion performance and stability. The abstract of the method is : (l) Four principal parameters regarding corner column spacing, column length, lower hull breadth and depth, etc. were selected as the parameters optimized. For the given range of these parameters, simulation designs are to be carried out to obtain principal dimensions corresponding to the parameters and satisfying the basic requirements and stability. Motion performance and economic efficiency are to be also calculated in these simulation designs. (2) Motion criteria for the operating condition herein differs from the ones for survival condition, which comply with the actual semisubmersible operations. The former regulates rig's motion at operating and the latter does the air gap and lower hull submergency at survival. (3) The most economical principal dimensions are to be selected from the groupe fulfilling the motion criteria. An example of optimization by adopting this method is also given, through the result of which effect of principal parameters on motion characteristics and economic efficiency was found.
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Hiroyuki ODA, Tomokazu ODA
Article type: Article
Pages
11-18
Published: June 30, 1983
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The submergence research vehicle has been operated in order to maintain the offshore structure or to detect a vein of ore in deep sea. For that purpose the vehicle has mainly operated with low speed. On the other hand, the ordinary submarine has been operated underwater with relatively high speed. These proper motion characteristics are not the same in point of operation. The characteristics of longitudinal motion of the ordinary submarine has been already presented by many papers. But, for the submergence research vehicle, such studies are not enough so that the authors tried to get the motion characteristics which should be considered at the initial design. Digital simulation of manoeuvring motions and numerical calculation of both static and dynamic stability were carried out on the basis of captive model test. Also, the authors checked the validity of simulation and that of model test by using the scaled model which is able to run underwater freely by the horizontal and vertical thrusters. It is found that the result of computer aided simulation showed a good agreement with that of free running test on the motion characteristics.
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Norimasa TAKAGI, Koich MASUDA, Masaaki SAKUTA, Wataru KATO
Article type: Article
Pages
19-29
Published: June 30, 1983
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This paper presents the practical prediction method of motion for the huge semisubmersible structure in waves The present method is based on the Hooft's assumption and modified his method. We have carried out forced oscillation tests, wave exciting force tests, and motion tests in beam sea condition. These results are compared with the calculation results from both the present method and three-dimensional singularity distribution method. As a result, the method presented in this paper predicts added mass coefficients, wave exciting forces and motion in waves practically.
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Hisayoshi TATANO
Article type: Article
Pages
31-42
Published: June 30, 1983
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This paper consists of the following four parts; 1) Sail camber as well as twist were measured for two sloop rigs and the effects of these two on sail performance was examined. 2) Comparisons were made with data of vertical wind velocity distribution and how the distribution on sail performance is affected. 3) Through a technique of using carriage of towing tank, model sail tests were performed and the aerodynamic center of pressure of sails was investigated. 4) A way to estimate sail performance was showed through above mentioned data.
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Norio TANAKA, Yoshiho IKEDA, Yasuo HADA
Article type: Article
Pages
43-51
Published: June 30, 1983
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A calculation method of solving the nonlinear coupled equations for ship sway, roll and yaw is proposed, in which the nonlinear terms of restoring moment, damping and cross-coupling dampings are taken into account. The nonlinear dampings are replaced by equivalent linearized forms with amplitude-dependent coefficients. The restoring roll moment is represented by an odd-power polynomial of roll angle. A perturbation method is applied to obtain the first-Order solution by extending Wright's method to the multi-degree ship lateral motions. The validity of the present method is confirmed through the comparisons with the roll experiments of two cylindrical models having strongly nonlinear GZ curves. Numerical examples are also presented to show that the coupling term of sway into roll has a considerable effect on the nonlinear roll response.
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Masashi KASHIWAGI
Article type: Article
Pages
53-64
Published: June 30, 1983
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This paper presents a theoretical method of calculating the hydrodynamic derivatives for sway and yaw of high speed ships oscillating in low frequency. A commonly known, practical procedure to deal with this problem is: (l) to evaluate the added mass and the radiation force by the strip theory and (2) to add the dynamic lift force without consideration on the free-surface effect. It is well recognized, however, that the strip theory can not evaluate correctly the free-surface effect in the low frequency or high speed range. On the other hand, Chapman has established a numerical method which may account for the advance speed effect on the hydrodynamic coefficients, but it is not certain yet whether Chapman's method is valid also for the case of sway and yaw oscillation. In this paper a new method is provided from the point of view of the generalized lifting-surface problem, assuming high Froude number and low frequency in addition to the thin-ship approximation. A series of sway and yaw oscillation experiments for a flat plate and a Wigley ship model are carried out at the Osaka University Ship Experiment Tank. Comparison of the test result with the existing and present theories are also discussed.
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Norio ISHII, Ichiro TANAKA, Akira KIMURA
Article type: Article
Pages
65-70
Published: June 30, 1983
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The numerical analysis of the boundary value problem with linearized free surface condition (Neumann-Kelvin problem) is presented. The wave resistances of Wigley model and a high speed container ship model (SR 138 model) are calculated. The results are compared with the experimental values and some theoretical solutions based on Michell's theory, double model source method and low speed theory. The solutions of the Neumann-Kelvin problem for Wigley model coincide fairly well with the experimental values. However, for the SR 138 model they are smaller than the measured values. These discrepancies are discussed by the comparison between calculated and measured wave contours.
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Hideaki MIYATA, Hisashi KAJITANI, Shinichi NISHIMURA, Hiroyuki TOMINAG ...
Article type: Article
Pages
71-82
Published: June 30, 1983
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Wave resistance is composed of linear and nonlinear components, and the nonlinear component must be taken into account for the evaluation of wave resistance of middle-speed ships. In this paper two methods of estimating wave resistance including the nonlinear component are presented, i.e., the method of characteristics and the method of the sum of wave height squared. The availability of the methods are examined by experiments with three kinds of series ship models, and the latter method that makes use of the wave profile near hull surfaces turns out to be generally successful.
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Akio ISHIKAWA
Article type: Article
Pages
83-90
Published: June 30, 1983
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In order to determine a two-dimensional cavitation free shape of a waterjet inlet, the computational method for one is given by making use of a boundary element method. Further, the contraction effect of a inlet by boundary layer displacement thickness is taken into account. This method enables us easily to obtain a cavitation free shape by trial and error procedure. Numerical examples are shown and it is suggested that the flow contraction by boundary layer thickness might be taken into account.
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Masatoshi BESSHO
Article type: Article
Pages
91-101
Published: June 30, 1983
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To study the extraction of energy from wave and current, it seems necessary to construct the theory of an oscillating thin wing more consistently, because existing theories, especially formulas of work-done or thrust, have no neat form owing to the leading edge suction in comparison with the case of wave resistance. In this paper, the theory of an oscillating thin wing in an infinite stream are expanded on the basis of acceleration potential. At first, homogeneous solutions which are the ones for homogeneous boundary condition are introduced. Secondly, two reciprocity theorems corresponding to Hanaoka's theorems are introduced and they enable us to calculate the strength of trailing vortex, leading edge singularity etc. from the said homogeneous solution as the same way as we can for the lift and moment by Munk's theorem. The thrust formula are deduced from the momentum theorem, so that the leading edge suction is included implicitly, and it, also the damping formula, is represented by quadratic form of the above introduced integral of homogeneous solutions. Lastly, under these preparation, the optimum problem, that is, optimum oscillation to obtain maximum thrust and extraction of energy from a uniform flow are solved easily in the most general formulation.
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Akikazu NAKAMURA, Wataru YASUKAWA, Hajime KAWAKAMI, Noriyuki KAMOI, Ta ...
Article type: Article
Pages
103-112
Published: June 30, 1983
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Moss type tank system consists of a spherical tank and a cylindrical supporting skirt. The spherical tank is an unstiffened thin shell structure with large R/t and the plate thicknesses are determined by buckling strength except the equator and tank bottom. The skirt is a cylinder stiffened by vertical stiffeners and rings except that the top part is unstiffened. The geometry determined taking the thermal deformation and various loads into consideration. The buckling strength is also the most important factor for the skirt. It is well known that buckling strength of spherical and cylindrical shells is highly sensitive to structural imperfection. Therefore, it is very, important to accurately predict this reduction factor due to the initial imperfection (imperfection factor) in order to establish reasonable safety factors and production talerances. This paper proposes design formulae for buckling strength of spherical tank and cylindrical skirt including the imperfection factor after investigating the effect of initial imperfection based on some papers previously published.
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Jun NAGASAWA, Kouhei MATSUMOTO, Kenji ARIMA, Hiroaki KADOU
Article type: Article
Pages
113-123
Published: June 30, 1983
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The conventional idea to protect a nuclear ship from collision is that her collision barrier has ability to absorb kinetic energy of the colliding ship by being destroyed during collision. However recently Gessellshaft fur Kernergiever wertung in Schiffbau und Schiffahrt m.b.H. (GKSS) of Germany was said to have developed the new type of collision barrier in nuclear ship, which had impact strength sufficient to destroy a colliding ship without damage itself. In Japan research on the new type of barrier, as the above mentioned one, began to be made experimentally and theoretically about five years ago. This research did not include investigation into the dynamic effect on strength caused by collision. This paper deals with the dropping collision tests to be carried out in order to study the effect of impact load on strength, by comparing the results of the dropping tests with the ones obtained from the quasi-static collision tests. The same bow models and collision models were used in the both dropping and quasi-static collision tests. The main conclusion are as follows: l) It was found from the collision tests, in which the same bow models collided against the conventional energy-absorbed barrier model and the newly developed one respectively, that; (i) The former model's deflection was larger than the latter's one. (ii) Acceleration occured at the former model is smaller than one at the latter model. (iii) Impact load measured at the former model was smaller and its period was longer than the latter model's one. 2) The same collapse mode was observed in the both dropping tests. This fact gives assurance that it is unnecessary to take into account of velocity of stress wave in the collision analysis of ship. 3) Measured impact load in the dropping test was larger than static load in the quasi-static collision test when models were deflected largely. This is supposed to be caused by the effect of strain rate which raises the yield point of steel.
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Masatoshi BESSHO
Article type: Article
Pages
125-132
Published: June 30, 1983
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The stress intensity factor in the elasto-dynamics has been defined from the stress near cracks and notches so that the accuracy of numerical computations might be necessary. The present report trys to define this factor from the variation of time mean of the potential energy of the crack surface as the same way as in the elasto-statics. It is found that this potential energy corresponds to Lagrangean, that is, the difference of the strain energy and kinetic energy, and that the amplitude of diffracted wave. Applying the theory, especially for a crack growing geometrically similarly, a simple formula are derived. Numerical results shows a slight difference from the usual value which has obtained from the stress near ends of a crack. The usual definition has been derived from a semi-infinite crack, so that it might not be correct for a finite crack and a dynamical case.
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[in Japanese], [in Japanese]
Article type: Article
Pages
133-137
Published: June 30, 1983
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[in Japanese]
Article type: Article
Pages
139-167
Published: June 30, 1983
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Article type: Appendix
Pages
169-171
Published: June 30, 1983
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Article type: Appendix
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Published: June 30, 1983
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Article type: Appendix
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Published: June 30, 1983
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Article type: Appendix
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Published: June 30, 1983
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Article type: Appendix
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App5-
Published: June 30, 1983
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Article type: Appendix
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Published: June 30, 1983
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Article type: Cover
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Published: June 30, 1983
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Article type: Cover
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Published: June 30, 1983
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