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Published: June 30, 1981
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Article type: Appendix
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Published: June 30, 1981
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Article type: Appendix
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Published: June 30, 1981
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Published: June 30, 1981
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Published: June 30, 1981
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Published: June 30, 1981
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Article type: Appendix
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Article type: Appendix
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Published: June 30, 1981
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Tomoo HANAWA
Article type: Article
Pages
1-11
Published: June 30, 1981
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This paper presents a study for the improvement of hu11 form design considering the effects of frame-shape. Based on the Separability Principle of Ship Form, a philosophy by which the frame-shape of aft-part are divided into two parts to make solving the problem easy, one is the part of main hull and the other is the part of skeg, was contrived. According to this philosophy, new formula for estimating viscous resistance and propulsive coefficient, and new method of designing C_p curve of aft-hull form, have been developed after analyzing the results of model experiments on various ship forms. A comparison of the calculated K, 1-wr and 1-t values with those by experiments show a good agreement in a wide range of ship type. Adequate shape of C_p curve without fear of separation of water flow even in case of large B/d ship form, is obtained by this method.
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Sumitoshi MIZOGUCHI, Ryo TASAKI
Article type: Article
Pages
13-23
Published: June 30, 1981
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Resistance tests in regular oblique waves were carried out with a model of S-175 container ship, which was used in computer exercise of the 15th ITTC, in IHI Seakeeping and Maneuvering Tank. The steering effects on ship motions were investigated in waves of heading angles;χ=-30°& 120°, by towing the model with and without the auto-pilot. The tests were done at zero mean drifting angle to coincide the test conditions with the assumptions of calculations. The mean heading angle was kept up to the given course angle by the auto-pilot steering and a soft yaw resisting spring in a vertical towing rod. The measured amplitudes and phases of the ship motions are compared with the calculations by O.S.M. using the non-linear roll damping coefficients derived from the free rolling tests at a given speed. The followings are conclusive results: 1. The effects of the auto-pilot steering on lateral ship motions are found in long quartering waves. 2. The calculated amplitudes and phases of the vertical ship motions are in good agreement with the measured ones except at χ=90°(beam waves). The measured amplitudes of the vertical ship motions at χ=90°are much greater than the calculated ones. 3. The calculated amplitudes and phases of sway and yaw show a good agreement with the measured ones except in long quartering waves. 4. The calculated amplitudes of roll are in good agreement with the measured ones except in long quartering waves. The calculated phases of roll are, however, much different from the measured ones except at χ=90°.
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Masamitsu ITO, Shosaburo YAMASAKI, Masamitsu OKU
Article type: Article
Pages
25-33
Published: June 30, 1981
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Polynomial coefficients of thrust and torque coefficients of well-known AU-CP 4 series CPP are obtained by multiple regression analysis as functions of pitch ratio, advance ratio and pitch angle. Coefficients at zero pitch angle are given in the paper. Three kinds of application are proposed and their numerical example are shown. First is design of optimum propeller. Propeller design charts like Bp chart etc. are usually used but their numerical treatment is very complexity in computerized design procedure. Employing Markussen's method, optimum propeller is easily obtained by the polynomial coefficients and numerical results show reasonable correspondence with those by Bp chart. The authors also appoint that initial pitch angle may become important design parameter in optimum CPP design. Second is estimation of open characteristics of CPP resembles to AU-CP 4 series and third is prediction of pitch angle for various CPP control method. In order to investigate adaptation to main engine, cavitation characteristics, vibration etc., designers must know pitch angle, thrust, torque and number of revolutions at each speed for planned control method. Estimation methods for N constant control, load control and DHP minimum control are proposed, by which designers can get necessary information easily at early stage of design.
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Tomoo HANAWA, Shigeyuki OGINO, Yoshitaka HASHIMOTO, Masaharu MUKAI, Yo ...
Article type: Article
Pages
35-43
Published: June 30, 1981
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The "Catamaran Stern" ship has a conventional fore part and an unusual stern form of catamaran type. This type of ship is expected to achieve very high fuel-saving, without experiencing propeller caviation, hull vibration due to propeller exciting force, air suction in ballast condition and other problems that are apt to occur to a ship with a single large low-speed-rotation propeller. In order to confirm the fuel-saving effect of this hull form and to better understand the design problems involved, we repeated the trial designing and tank testing. As a result, we have confirmed that the "Catamaran Stern" ship saves 15% more fuel than the conventional single-screw ship with the same principal dimensions, deadweight, and service speed.
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Tetsuro IKEBUCHI
Article type: Article
Pages
45-53
Published: June 30, 1981
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In order to predict theoretically the motions and mooring forces of a body moored by the non-linear mooring system in irregular sea waves, we have to use the equation of motion in the time domain. Therefore the hydrodynamic coefficients involved in that equation must be ones in the time domain. This paper presents a calculation method of the hydrodynamic coefficients in the time domain. The hydrodynamic boundary-value problem on a two-dimensional body is formulated on the basis of the linear potential theory, using the impulse response function which Cummins first proposed, and the problem is solved making use of the Green's function. A numerical example for a circular cylinder is presented. And in order to confirm the validity of the present method, the calculations of the force of forced oscillation and the hydrodynamic coefficients in the frequency domain for the same cylinder using the hydrodynamic coefficients by the method have been carried out and the results were compared with those by the established method in the frequency domain. It is found that the results are quite satisfactory.
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Yoji HIMENO, Taketoshi OKUNO
Article type: Article
Pages
55-62
Published: June 30, 1981
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The present paper describes an experimental investigation concerning the nonlinear lift characteristics of a thick symmetric airfoil at zero incidence where the lift curve slope turns to be negative. Detailed studies on the flow around the airfoil and the surface pressure distribution show that the nonlinear behavior is related to the flow separation near the trailing edge. While in laminar flow no separation is found, a large separated region is observed near the end of the airfoil in turbulent flow. The pressure distribution in turbulent flow also differs much from the one in laminar flow. The separation near the body end makes the pressure difference between both sides of the airfoil not restricted in the tail region, but spread over the entire chord length.
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Yeun Junn LIN, [in Japanese], Hisashi KAJITANI, Hideaki MIYATA, Susumu ...
Article type: Article
Pages
63-75
Published: June 30, 1981
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To clarify the physical mechanism of the interaction between hull and propeller many kinds of experiments have been carried out with geosim models of 2.5m and 10m. They are measurement of hull surface pressure and wave height on towing and selfpropelling conditions and partly on T=0 condition, measurement of waves generated by a propeller and measurement of thrust, torque and waves when propeller-position is shifted aftward. The obtained results can partly be explained by the theoretical calculation of the previous paper; however, it is also clear that much more complicated phenomena of interaction exist. Advantages and disadvantages of the potential theory are discussed. The increment of resistance due to the action of a propeller (thrust deduction) is not independent of advance speed, because it is influenced by the interaction of waves. The free surface flow and the effect of wake distribution must be considered in addition to Lagalley's force for the improvement of our understanding of the interaction.
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Masakatsu MATSUISHI, Setsuo IWATA
Article type: Article
Pages
77-87
Published: June 30, 1981
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The authors have developed a composite prestressed concrete steel structural module for the supporting elements of offshore structures. The composite structural module is composed of biaxially prestressed concrete and a steel frame surrounding the concrete. The prefabricated composite structural modules are joined together to build a main structure by welding the steel frames. The joint between the composite modules is simpler and more reliable than those of conventional concrete structures. In the previous paper, the authors carried out both experimental and theoretical investigations into the stresses and deformation of the composite modules during prestressing. In the present paper, the authors carried out both experimental and theoretical investigations into the strength of the composite module under shearing force, bending moment or combined bending and shear. Structural properties of the module were clarified through the experiments. The authors developed methods for the ultimate strength analysis and the nonlinear analysis using the finite element method. A comparison of calculated and observed results shows good agreement. Based on this comparison, the fundamental properties of the composite were clarified.
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Koichi OSHIMA, Hiroo OKADA, Yoshio HUKUMOTO
Article type: Article
Pages
89-97
Published: June 30, 1981
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In this paper, the behaviour and the strength of simply supported plates (aspect ratio α=1,2 and α=∞ (infinitely long plates) having in-plane constraint in the transverse direction under combined loads of compression and hydrostatic pressure are theoretically investigated following the previous studies. At the same time, effects of aspect ratio of plates on the behaviour and the strength are also discussed from these results including those for plates of α=3 and 4. Results obtained in this study are summarized as follows: 1) Carrying out the analyses based on equations deduced to pursue the elastic behaviour of plates (α=1,2 and ∞) whose long sides are transversely immovable (ey=0), characteristics of behaviours including buckling phenomena are clarified. 2) The compressive strength of such a plate is calculated in the same way as the previous paper, and characteristics of the compressive strength and the collapse mode of the plates (α=1,2 and ∞) are clarified. 3) From comparison between above results including those for plates of α=3 and 4 and results for the case of plates having no in-plane constraint (Py=0) in the previous paper, it is found that the behaviour of the plate for each case is different but the effects of aspect ratio of the plate on the changes of the buckling and the compressive strengths with hydrostatic pressure for each case are generally similar.
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Hideyuki SHURI, Tomomichi KURIHARA
Article type: Article
Pages
99-109
Published: June 30, 1981
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The SEA (Statistical Energy Analysis) method has recently been used to estimate sound and vibration transmission through complex steel structures such as ships. The authors examined the application of this method to prediction of the sound and the vibration levels in two steel structure models, and obtained results summarized as follows: (1) In addition to the resonant power flow, the non-resonant one should be considered for the power transmission through partition panels of adjacent air spaces. (2) Two kinds of power dissipation should be considered besides the internal one. One is the power lost from the model across the boundary of the neighboring structures and the other is the power radiated as sound into the free space. In the calculation, these power losses are taken into account as increments of the internal loss factor of the elements. The values of the internal loss factor for the panel elements used in the calculation were obtained from empirical measurements with steel panels hanged freely in the air. (3) For the sound pressure levels and the vibration levels, the agreement between the calculation results and the experimental ones of two different models was found to be good. (4) The effect of absorption materials (for example glass wool) on the reduction of the sound pressure levels in the models was experimentally investigated and clarified.
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[in Japanese]
Article type: Article
Pages
111-115
Published: June 30, 1981
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[in Japanese]
Article type: Article
Pages
117-122
Published: June 30, 1981
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Article type: Appendix
Pages
123-125
Published: June 30, 1981
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Article type: Appendix
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Article type: Cover
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