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Tadaaki Kaneko, Katsuro Kijima
Pages
1
Published: 2001
Released on J-STAGE: June 30, 2003
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When we consider manoeuvring performance of a ship which has a close relation to the hydrodynamic forces acting on a ship hull, we need to turn our attentions to not only deep water but also shallow water such as harbors and canals. Therefore, it is necessary to establish the prediction method which can take the effect of shallow water into account in order to estimate the hydrodynamic forces. In this paper, applying the slender body theory with the dispersive vortex model, we investigated the hydrodynamic forces acting on a ship hull in shallow water.
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Mirel Nechita, Hidetsugu Iwashita, Shinya Tominaga, Satoshi Tanaka, Ka ...
Pages
2
Published: 2001
Released on J-STAGE: June 30, 2003
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The bluntness effect of the hull form is investigated by comparing numerical results with experiments for a Series-60 slender model (C
b=0.6) and a blunt model (C
b=0.8). The numerical method used in this study is a desingularized Rankine panel method which enables exact treatment of the steady wave field in the computation of the unsteady problem. The unsteady problem is solved taking into account the influence of the fully nonlinear steady wave field through the free surface and body boundary conditions. Numerical results for the hydrodynamic forces are compared with experimental data and strip method. Discussions are made on the bluntness effect of the two hull forms on hydrodynamic forces, steady and unsteady wave fields.
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Hidetsugu Iwashita, Yohei Hidaka, Kenichi Kishimoto, Mirel Nechita
Pages
3
Published: 2001
Released on J-STAGE: June 30, 2003
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The measurement of unsteady waves in a towing tank is simulated numerically and the side wall effect is discussed especially for the measured unsteady waves in the low frequency range. Unsteady waves measured by Ohkusu’s method are now very useful and unieque to validate the highly advanced computation methods for seakeeping. Usually the measurments are carried out for high frequency range, escaping from the side wall effect of a towing tank due to propagating waves in front of the ship model. The measurment itself, however, is possible even for the low frequency range allowing some side wall effects of the towing tank. If the effect is made clear, the obtained experimental data can be used as an index to validate computations. The numerical simulation is performed simplifying the complicated ship motions by a pulsating point source. The space fixed coordinate system is adopted and the point source is accelarated arbitrary corresponding to the time history of the velocity of the towing carriage in the experiment. Two results, with and without side wall, are compared and the side wall effect is discussed.
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Yusaku Kyozuka, Takeshi Kasa, Masaru Inada
Pages
4
Published: 2001
Released on J-STAGE: June 30, 2003
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Observation of the coastal current by an Acoustic Doppler Current Profiler (ADCP) was conducted at the Tsuyazaki Ocean Station of the Research Institute for Applied Mechanics (RIAM), Kyushu University, 2 km offshore of Fukuoka, Japan. The depth of the water is about 15 m at the station and an ADCP was put on the sea bottom in the center of the station. The main interest of the observation was the vertical structure of the coastal current, and the current was measured at about 36 layers of 0.5 m thickness in the vertical plane every hour for 30 days in September 2000. Regular measurement data were provided by the RIAM on wind, tide level, waves and water temperature and the effects of wind current, density current and tidal current on the measured current data are discussed.
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Renchuan Zhu, Kimio Saito, Hisashi Nobukawa
Pages
5
Published: 2001
Released on J-STAGE: June 30, 2003
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A nonlinear simulation is carried out for the motion of the inviscid, incompressible fluid in a three-dimensional tank of barge for lithium extraction from seawater that is subjected to forced oscillations. According to a conceptual design of the barge, seawater flows into the tank from suction valves on the inner bottom of the barge, and then passes through the piled granulated adsorbent and it is discharged out of the tank by drain pumps on the side hull of the barge. In order to solve the problem associated with the inhomogeneous fluid domains of seawater and granulated adsorbent, the general boundary element method (BEM) is extended. From the numerical results obtained by the present method, the effect of forced oscillations on the fluid motions in the tank (sloshing) has been shown.
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Nobuyoshi Fukuchi, Takeshi Shinoda, Yoshimi Uraguchi, Tomohiro Ryu
Pages
6
Published: 2001
Released on J-STAGE: June 30, 2003
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The countermeasures should be taken to cope with the impact of oil pollution that is related to the influence on the coastal ecosystem. Accordingly, the relation between the degree of oil pollution and the coastal ecosystem has to be clarified by taking some appropriate step. For this purpose, an analytical model on the coastal ecosystem is established by using the way of
System Dynamic in which phytoplankton, zooplankton, nekton, detritus and dissolved oxygen are assumed to be governing factors in this environmental problem. And a numerical simulation on coastal ecosystem in an enclosed area of
Hiroshima bay is carried out in varying the quantity and kind of spilt oil, the season of outbreak of accident, the oil gathering quantity. From the calculated results, the impacts of oil pollution on coastal ecosystem can be grasped considerably.
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Yasuaki Doi, Kuniji Kose, Eiichi Baba, Shinnosuke Oharu, Masayoshi Kom ...
Pages
7
Published: 2001
Released on J-STAGE: June 30, 2003
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These days, the red tide plankton of Heterocapsa circularisquama has done mortal damage to the oyster culture which is one of the famous marine product industry in Hiroshima. In order to cope with the damage of red tide plankton, the present study proposes to develop the real time monitoring system which enable to observe the movement of sea water condition. Eta-shima Bay is selected for the observation because of the location of oyster culture farm and geographical conditions. Two observe positions are selected from which the measured data is sent to the station on the ground. Depending on the condition, a ship is prepared for the measurement of nutrients and cell density of planktons. The monitoring was carried out in summertime of 1999 and 2000. The characteristic phenomena in Eta-shima Bay was observed by the present system.
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Yasuaki Doi, Kei Morishita
Pages
8
Published: 2001
Released on J-STAGE: June 30, 2003
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Numerical simulation of tidal current of an enclosed sea is carried out considering the effect of oyster rafts. Multilevel model is employed for the flow simulation. About 600 chains of oysters suspended from a raft are replaced by the resistance term distributed uniformly in the area where the oyster rafts locate. The basic equations are solved by finite difference method, where the convective terms are given by the third order upwind difference and other terms are given by the second order centered difference method. Eta-shima Bay is selected for the simulation. In order to compare with the simulated results, path lines of flouting buoy was measured by use of GPS. Through the comparison with simulated and measured results, it is concluded that the present method has a merit to simulate the tidal current in Eta-shima Bay. Comparison of simulated flow pattern with and without the oyster rafts shows the effect of rafts on the current especially the residual flow.
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Takenori Hiraoka, Hisashi Kajitani
Pages
9
Published: 2001
Released on J-STAGE: June 30, 2003
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The pressure on a NACA0012 and its modified aero-foils is measured in a circulating water channels. The so called Nakatake and Andou’s SQCM method that comprises sources(S) on foil surfaces with Lan’s quasi continuous vortex lattices on its camber plane is employed to analize the surface pressure of the above foils. Viscous effect cannot be neglected as to the measured pressure on the two-dimensional aero-foils of 200mm chord under 1∼1.75m/s flow velocity (
Rn ≈ 2∼3.5×10
5). On the other hand the viscous effect is almost negligible except for tail ends as to the low aspect three dimensional foils of 500mm chord (
Rn ≥ 5×10
5) through which the availability of the SQCM analysis is discussed.
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Masamitsu Ito
Pages
10
Published: 2001
Released on J-STAGE: June 30, 2003
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Unsteady boundary layer characteristics on rotating propeller blades are calculated numerically. Unsteady boundary layer equations are simplified with quasi-three-dimensional approximation to achieve computational efficiency. A relatively simple, yet efficient and accurate finite difference Oskolkov’s scheme is extended to three-dimensional calculations and adopted. Accuracy of the code was validated with the calculation of oscillating flat plates. Significant unsteady effects on boundary layer characteristics are calculated especially when strong unsteady separation occurs on blade surface. Almost no discrepancy is predicted between unsteady and quasi-steady calculations if no strong separation is existing.
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Shigeru Hayashita
Pages
11
Published: 2001
Released on J-STAGE: June 30, 2003
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It is necessary to estimate the drag of propeller shaft at the design stage of the high speed craft. In order to investigate the effect of attached angle and diameter of propeller shaft to the drag, hydrodynamic forces acting on shaft of prismatic body were measured by load cell. Measured drag was not estimated by the formula which is used to estimate the drag of inclined circular cylinder.
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Tetsuo Nagamatsu, Keisuke Yoshinaga
Pages
12
Published: 2001
Released on J-STAGE: June 30, 2003
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An observation of microbubble flow has been made for a full-scale ship “NANSEI-MARU” which is a training ship of Kagoshima University. In order to generate microbubbles, air is ejected from many small holes on bendable pipes, of which section is like a saddle shape. The bendable pipes are fitted horizontally on the portside hull at bow and another bendable pipe along the girth of SS.8 at the starboard bottom. It was observed by underwater video camera that microbubbles flow along the bottom surface from bow until at least SS.3.
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Agoes Priyanto, Arif Fadillah, Renchuan Zhu, Kimio Saito
Pages
13
Published: 2001
Released on J-STAGE: June 30, 2003
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In Kalimantan of Indonesia, the coal is transported by using coal barge through a river into a large ship at open sea. Recently, in order to improve the existing loading/unloading system, a new semi-submersible structure has been proposed which has an advantage of minimum motion responses in waves and will make it quicker and easier to transship coal from barge into deep draft bulker. In this paper, following the former paper, the wave performances of a new type structure including the effect of a large ship alongside have been discussed. The united 2D dynamic model of a semi-submersible structure and a coal barge has been considered and the theoretical calculations have been compared with the experimental ones.
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Abdul Muis, Eiichi Baba, Indrayati Subagio, Muryadin
Pages
14
Published: 2001
Released on J-STAGE: June 30, 2003
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The coal resource in kalimantan reaches 31.6% of the Indonesian overall source of about 36.3 billion tons. The coal demand for local and export has increased annually. This increase in coal production has affected the demand in transportation system, especially for river transportation system. However transportation system on the river has its own problems. Therefore improvement on the transportation system requires considerations in some aspects due to river conditions. A pusher barge system is recommended in this study to overcome these constraints through its distinct features such as good maneuver at curved river and seaworthiness in open sea.
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Seiji Iwamoto, Seiichi Takeda, Kimihiko Ueno, Hiroyuki Oda, Masamitsu ...
Pages
15
Published: 2001
Released on J-STAGE: June 30, 2003
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The purposes of this study are as follows: 1) Construction of the mathematical model for ship monoeuvring motion in consideration of roll motion. 2) Construction of systems for measurement and control of the ship motion using MATLAB/Simulink language. 3) Experiment of the course keeping and reduction of roll motion with the optimal regulator and with the control system by decoupling control theory. A series of the study from mathematical model construction to tank test with the UMITAKA-MARU model has been carried out from the viewpoint of practical application, we show the results.
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Treatment of Friction and Non-linearity
Hiroshi Isshiki
Pages
16
Published: 2001
Released on J-STAGE: June 30, 2003
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In the previous paper, a new method to apply Hamilton’s principle to numerical solution of initial value problems in mechanics was discussed. In this method, time and space variables are treated equally, and initial value problems are treated as boundary value problems. The method was applied to linear conservative problems for the sake of simplicity. In the present paper, the method is extended to problems with friction and non-linearity. Some numerical calculations are conducted, and reasonable solutions are obtained.
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Changhong Hu, Nobuyoshi Fukuchi
Pages
17
Published: 2001
Released on J-STAGE: June 30, 2003
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In this paper, a large eddy simulation (LES) method is presented which can calculate incompressible, unsteady, three-dimensional, viscous and turbulent buoyancy-driven flow fields. This method is a finite difference method with second order precision of both time and space, using Smagorinsky SGS model to treat the turbulence effect. Two examples, Rayleigh-Benard convection and convection in a side heated and cooled rectangular box, are numerically simulated. The difference of using SGS viscosity with and without a buoyant term, are studied. The computed results are compared to other simulation results and experimental data.
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Nobuyoshi Fukuchi, Go Okahata
Pages
18
Published: 2001
Released on J-STAGE: June 30, 2003
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The dynamic behaviors of structures in principle of a non-conservative system, such as a submerged thin shell structure under follower type load in the circulatory system and a column under periodic load in the in-stationary system, may assume various nature phenomena. This paper deals with characterizing the dynamic stability of the structures in non-conservative system using Lyapunov exponent, in order to clarify the structural mechanisms of dynamic motions and critical threshold. A submerged thin shell structure under follower load with disturbances as an example of Duffing equation-type problem, and a column under periodic load for instance of Mathieu equation-type problem are investigated herein to presume the process up to unstable state by Lyapunov exponent as a stability index.
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Hai Gu, Mitsuru Kitamura
Pages
19
Published: 2001
Released on J-STAGE: June 30, 2003
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Submodeling method is used to achieve efficiency in finite element analysis when details are required in subregions of a large structure. Various implementations of this technique can be found in literature, and in most of them displacements are driven variables. However, by using recovery procedure, the accuracy of stresses can be improved significantly, therefore, in this paper, recovered stresses will be employed as driven variables. Stress method and displacement method are compared in numerical investigation. It will be shown that there do exist situations where using stresses as driven variables may lead to better result than using displacements.
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—Strength of Cruciform Fillet Welded Joint—
Takayuki Kawano, Katsuaki Inoue, Katsumi Kawaichi, Hiroshi Yajima, Yun ...
Pages
20
Published: 2001
Released on J-STAGE: June 30, 2003
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Tanks of a spherical tank type LNG carrier are supported by the cyrindical shells by the name of “skirt”. On the one hand aluminium (Al) alloy (A5083) having good low temperature properties is used for the upper part of this skirt, on the other hand stainless steel (SUS) having low thermal conductivity is used for the lower part. In this case, because Al and SUS are not able to be welded directly, therefore Al/SUS STJ is used to connect these two kinds of materials. Recently, at Nagasaki Research & Development Center, Mitsubishi Heavy Industries, LTD., the vacuum roll bonding method for producing a new-type Al/SUS STJ industrially is developed and investigated instead of the explosive welding method. In this paper, in order to quantify the fracture strength of this new-type Al/SUS STJ produced by the vacuum roll bonding method, a series of round bar tension tests and cruciform welded joint tension tests were performed by using the three kinds of STJ produced under the three conditions. As a result of the investigations described above, all three kinds of Al/SUS STJ used for tests were certified to be practicable for the tank skirt part of a spherical tank type LNG carrier from the viewpoint of the fracture strength.
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—Fracture Strength Analysis for Cruciform Fillet Welded Joint—
Katsumi Kawaichi, Takayuki Kawano, Yoshiaki Inoue, Naoaki Fujiwara, Hi ...
Pages
21
Published: 2001
Released on J-STAGE: June 30, 2003
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Tanks of a spherical tank type LNG carrier are supported by the cyrindical shells by the name of “skirt”. On the one hand aluminium (Al) alloy (A5083) is used for the upper part of this skirt, on the other hand stainless steel (SUS) is used for the lower part. In this case, because Al and SUS are not able to be welded directly, therefore Al/SUS STJ is used to connect these two kinds of materials. Recently, at Nagasaki Research & Development Center, Mitsubishi Heavy Industries, LTD., the vacuum roll bonding method for producing a new-type Al/SUS STJ industrially is developed and investigated instead of the explosive welding method. In this report, in order to investigate the fracture strength and breaking type of this new-type STJ in more detail, three-dimensional elastoplastic FEM analysis was performed. As a result of the investigations described above, this new-type Al/SUS STJ can show the enough strength when all breaking types occur, because all kinds of fractures are able to occur only after the Al alloy part just on the faying surface is deformed sufficiently.
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Koji Setta, Daisuke Yanagihara, Masahiko Fujikubo
Pages
22
Published: 2001
Released on J-STAGE: June 30, 2003
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In this paper, the influences of the strain-hardening rate, stress-strain relationship, welding residual stress, reduced strength in heat affected zone and taper cross-section on the buckling/plastic collapse behaviour of aluminum stiffened plates are investigated performing FEM analyses. The simplified method to estimate the ultimate strength of aluminum stiffened plates is developed considering observed influences.
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Motomichi Yamamoto, Hiroshi Yajima, Masayoshi Kurihara, Ryuji Masumoto ...
Pages
23
Published: 2001
Released on J-STAGE: June 30, 2003
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When buckling collapse takes place in structural steel members, large compressive strain deteriorates the ductility and fracture toughness of the material at the concave side of buckling deflection. Therefore cracks may easily initiate and propagate at the concave (compressive) side of buckling deflection. In this paper, in order to quantify the deteriorating effect of the large compressive strain on the fracture toughness of steels, a series of CTOD tests were performed on three kinds of steels (490MPa-class high tensile steel plates). As a result of the investigations described above, the following conclusions were obtained: (1)Fracture toughness (δc) is deteriorated extremely and trasition temperature shifts to very higher side with increasing the compressive prestrain. (2)From investigation results of brittle fracture surfaces both of CTOD specimens and V-notch Charpy impact test specimens, regardless of the kinds of the steels, the rugged fracture surfaces become flat with increasing the compressive prestrain. (3)The equations to be able to estimate the fracture toughness of the steels experienced large compressive strain by using the results of V-notch Charpy impact test and tension test for the steels prestrained in compression are obtained.
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Junichi Katsuta, Kazuyoshi Kawano, Tsuyoshi Kato, Kentarou Fujii
Pages
24
Published: 2001
Released on J-STAGE: June 30, 2003
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In this study, the authors have investigated the ways in regard to bending process of the pillow, the saddle, and the twisted shape shells. The result of these questionnaires that even if object is the same shape shell, there are the many ways for bending process is obtained. And we have developed the simulator system using PC for bending process by imitative heating. This simulator system is used 3-dimentional elastic analysis without thermal conduction analysis by FEM, and can be used acquirement tool for skills of line heating to replace experiences which take a lot of time and cost. The results of simulation are the same as the results of examination approximately.
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Hiroshige Kitada, Masakazu Uenishi, Tsutomu Fukui
Pages
25
Published: 2001
Released on J-STAGE: June 30, 2003
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In the latter half of 1980’s, YP40 steels by TMCP were newly developed and have been utilized for various types of large vessels. In this paper, application assessment on the YP40 steels in the NK-classed large vessels is discussed. Then the assessment comes to the following conclusions: (l) The YP40 steels have been widely applied to the NK-classed large vessels. In particular, the YP40 steels-applied bulk carriers (number of ships-based) reaches as far as 50%. (2) Heeding points on design and workmanship in way of hatch opening corner and hatch side coaming end are obtained from the damage review of the large bulk carriers applying the YP40 steels. (3) It appears that no unusual damages due to the application of the YP40 steels occur in the large container carriers and oil carriers.
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Masayoshi Oka, Masaru Hirakata, Yutaka Hashizume, Takeshi Miyamoto
Pages
26
Published: 2001
Released on J-STAGE: June 30, 2003
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Free-Fall Lifeboat was developed as a life saving system that ensured quick and safe evacuation from a wrecked ship by sliding / dropping from a launching system equipped on the deck to a sea surface. Fundamental research is required in order to establish design technology of free-fall lifeboat of this type. For the purpose of constructing a free-fall lifeboat made of FRP, and for improvement of structural safety of life-boat, “Research and Development Project of a Free-Fall Lifeboat System” was promoted by the Shipbuilding Research Association of Japan. In this project the experiment used a 6/8 large-scale model was carried out, and useful data was obtained, such as hydrodynamic impact pressure and structural response at water entry. Furthermore, it was examined structural strength by FEM analysis. This report describes results of drop tests and FEM analysis. Resulting from this R&D, it becomes clear that relation between the impact load acting on the hull surface and structural response.
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Hideyuki Seto, Jinichi Nakatsuka
Pages
27
Published: 2001
Released on J-STAGE: June 30, 2003
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This paper describes a theoretical approach for hydroelastic responses of a very large floating circular plate in regular waves. Eigenvalues and eigenmodes of a uniform circular plate with free edge in dry condition are determined analytically and modal hydrodynamic loads are solved by the Rayleigh-Ritz method of domain decomposition type. Then modal approach is applied to the body-wave interactions. Calculated results have been compared with those for a rectangular counterpart.
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Koji Kagawa, Masahiro Maeda, Kazutaka Toyota, Yukitaka Yasuzawa, Naoki ...
Pages
28
Published: 2001
Released on J-STAGE: June 30, 2003
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This paper presents an optimal design method of the structural vibration using artificial neural networks. Neural networks are used for the calculation of the objective function and the sensitivity analysis in the design optimization which needs enormous calculations. The optimum solution can be searched on the curved surface composed of the objective function calculated by neural networks. The presented method is applied to the optimization of the natural frequency of the superstructure. It is coufirmed that the presented procedures are efficient and practical for simplifrcation and acceleration of the iterative calculations of the objective function and sensitivity in the design optimization.
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Mitsuru Kitamura, Tetsuya Uedera
Pages
29
Published: 2001
Released on J-STAGE: June 30, 2003
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Zooming finite element analysis is introduced in order to remove this drawback with efforts of sensitivity analysis. Sensitivity analysis is used for estimating the boundary condition for the zooming region. Since a different mesh sub-division from the initial analysis can be used for zooming analysis, it is possible that optimum design is proposed based on the more accurate stress analysis and stress evaluation points are different from the initial analysis. The proposed method are applied to 499 G/T ship structure and good performance is shown in this paper.
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Mitsuru Kitamura, Takakazu Nakamori
Pages
30
Published: 2001
Released on J-STAGE: June 30, 2003
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There are unique operators and many parameters in Genetic Algorithm which are used to find the optimum design in engineering problems. However, a solution does not converge well and proper design plan can not be obtained if those values are not adequately selected. In this paper, it is studied that the value of the penalty coefficient at the initial stage should be computed automatically based on the objective functions and constraint conditions for all individuals at the initial generation. The generation at which the penalty coefficient becomes constant is also investigated.
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(Part 3, Optimization of Hull Weight with Genetic Algorithm)
Hiroshi Furuno, Mitsuru Kitamura
Pages
31
Published: 2001
Released on J-STAGE: June 30, 2003
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The authors have developed an initial hull structural planning and hull weight optimization system for double hull tankers. This system can estimate hull weight and search for a design candidate that minimize the hull weight from a number of candidates. In this paper, an initial hull structural planning and hull weight optimization system with Genetic Algorithm (GA) on account of expansion of kind of design variables and searching of the wide field is developed. The system is based on the design process traditionally used in shipyard, and hence; there is difficulty in satisfying the required cargo capacity. In order to remove this drawback, a method is proposed with aid of bit arrangement for genes in GA optimization process. The hull structure optimization system in initial planning is created and good numerical performance is shown here.
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Yasuhisa Okumoto, Kouhei Murase, Morinobu Ishiyama, Sayuri Yamagishi
Pages
32
Published: 2001
Released on J-STAGE: June 30, 2003
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This paper has picked up the assembly process of hull construction as an example of the detail scheduling to establish an intelligent system for it, considering the movement of individual person as a human based system. The assembly process was assumed as a conveyer system with plural lines where a series of process-such as arrangement of steel materials, fitting, welding, and inspection-are carried out at constant tact time one by one by plural persons. The workers may move to another line when they have finished their own works at a stage. The analysis was made by a combination of simple linear equations, and a computer program was developed. The calculation result using a test data showed that the system was useful and effective.
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