Journal of the Japan Society of Naval Architects and Ocean Engineers
Online ISSN : 1881-1760
Print ISSN : 1880-3717
ISSN-L : 1880-3717
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  • Go Okahata, Kazuki Yabushita
    2018 Volume 28 Pages 1-12
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    We present a new technique determining the form factor from resistance test results by using the sparse modeling. In the present method, the total resistance coefficient is approximated by a straight line and a high-order polynomial expression. The straight line and the high-order polynomial expression represent a viscous resistance and a wave-making resistance, respectively. The inclination of the straight line is only a function of the form factor. We determine the inclination and coefficients of the polynomial expression by means of sparse modeling. The present method is applied to some SR resistance test data under full load and ballast conditions, and the obtained form factors are in agreement with the values presented in the SR reports.

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  • Kazuhisa Yagi, Naoki Osawa, Satoyuki Tanaka, Kazuhiro Kuroda
    2018 Volume 28 Pages 13-26
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Full-scale fatigue tests of the land structure's T-shaped tubular welded joints are conducted. Three-dimensional finite element (FE) fatigue crack propagation (FCP) analyses based on VCCM with tetrahedral elements are performed in order to obtain the reference SIF solutions. The preciseness of the FE FCP analyses is demonstrated by comparing calculated and measured crack propagation behaviors. Hot spot stress (HSS)-based fatigue assessments are carried out by using various fatigue design codes for tubular joints, and the safety margin of each HSS determination techniques are compared. The crack propagation lives are also predicted by carrying out FCP analyses based on Mk factor method. HSS determination techniques examined in the fatigue assessment are adopted to determine the stress concentration factor (SCF) and the degree of bending (DOB) in Mk factor calculations. It is found that the Mk factor-based FCP results show good agreement with the FE FCP results and the measurements when the HSS determination technique with the smallest safety margin is chosen. Based on these results, the method for selecting SCF and DOB calculation procedure for Mk factor-based FCP analysis is proposed. It is also shown that the difference between the fatigue test results and the HSS SN-based fatigue assessment results becomes smaller when the SIF estimated by Mk factor method agrees with the SIF calculated by the FE fracture analysis.

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  • Jun Umeda, Hiroki Goto, Toshifumi Fujiwara, Tomoki Taniguchi, Shunji I ...
    2018 Volume 28 Pages 27-36
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Some active controls were proposed to maximize the power production for the point absorber type wave energy converter (WEC) with a linear generator. However, proposed conventional controls have some problems, e.g. constraint conditions cannot be considered. Model predictive control (MPC) has attracted attention as an alternative method to solve these problems. In this paper, the performance of the MPC for the WEC with the linear generator was evaluated by experiments and numerical simulations. In the experiments in regular waves, the MPC performance was comparable to the conventional control of the power production amount reasonably. Furthermore, the MPC was more effective than the conventional control in irregular waves which has broadband spectral distribution. The numerical simulations in the irregular waves analyzed three characteristics of the proposed MPC. Firstly, it was investigated how much the power production decreased due to wave predictive error. Secondly, the best predictive horizon of the proposed MPC was investigated. The simulation result showed the predictive horizon of the MPC needs to be longer than the averaged wave period in irregular waves. Finally, performance of the MPC was compared with that of the conventional control under displacement constraints. It was confirmed the MPC presented in this paper was more effective than the conventional control under the displacement constraints.

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  • Mariko Kuroda, Ken Takagi
    2018 Volume 28 Pages 37-43
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    So far, added resistance in irregular waves is generally evaluated as a mean value in short term by means of the calculation in frequency-domain. The power spectrum of waves and the frequency response of added resistance in regular waves are used in the calculation, and the added resistance in regular waves is assumed to be proportional to square of wave height based on the 2nd-order wave theory. However, it has been found from tank tests that the added resistance in regular waves is not always proportional to the square of wave height. The major reason is considered that the influence of the hull form above the waterline on the added resistance in waves varies depending on a wave height. Therefore, it is not clear if the 2nd-order theory gives a good estimation for the slowly-varying added resistance in irregular waves.

    In this paper, higher order components are considered to estimate the slowly-varying added resistance in irregular waves with the wave height effect. As a result, the slowly-varying added resistance in waves with the consideration of wave height effect is mathematically expressed as the 4th-order component. The estimated results are compared with tank tests, and it has been concluded that the 4th-order component greatly contributed to improvement of the accuracy.

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  • Hideki Miyazaki, Yasushi Kitagawa, Yoshiaki Tsukada, Michio Ueno, Haru ...
    2018 Volume 28 Pages 45-52
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    On 13 November 2009, suddenly an accident occurred in which a fast RO/RO ferry was greatly inclined to the starboard side in quartering sea. The Japan Transport Safety Board (JTSB), Ministry of Infrastructure, Land, Transport and Tour-ism looked into this incident, and reported the results of survey. That report was including estimated conditions of ship at the incident and wave, wind so on. In order to take measures, clarification about mechanism of this phenomenon is important. In order to know what had happened, the authors carried out a model experiment reproducing the incident at Actual Sea Model Basin, in National Maritime Research Institute, Japan.

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  • Takao Yoshikawa, Masahiro Maeda, Kimihiro Toh, Takuya Ishibashi, Mizuk ...
    2018 Volume 28 Pages 53-61
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    When colliding and grounding of ship, fracture may occurs in the hull structural member, which may cause serious accidents, such as environmental pollution and the loss of lives/cargo due to damage of the ship. To examine the safety of the ship for the collision using experiments will take much time, cost, and effort. Therefore, it is necessary to confirm it by a numerical calculation.

    In the collision analysis using the finite element method (FEM), it is judged that the rupture occurs if the equivalent plastic strain of an element exceeds the critical value, and then the element is generally erased. In the meantime, it is known that the equivalent plastic strain at the ductile crack initiation will decrease with an increase of stress tri-axiality. Therefore, the accuracy of fracture analysis is expected to be improved by taking account of the tri-axial effect on fracture strain.

    In this paper, to investigate the effect of stress tri-axiality on the equivalent plastic strain at the ductile crack initiation, the tensile tests of round bar with notch of different acuity were carried out for the three kind of steel with different strength. And, the rupture calculations for the specimens with a stress concentration part were performed with and without taking account of the fracture strain under tri-axial stress condition. Moreover, the calculation accuracy and the effectiveness of such calculations were clarified by comparison of experimental results.

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  • Kimihiro Toh, Masahiro Maeda, Daisuke Yanagihara, Takao Yoshikawa
    2018 Volume 28 Pages 63-74
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Nowadays, the static ore pressure can be evaluated with the adequate accuracy by the explicit calculation formula, whereas as for the dynamic ore pressure, the exact calculation formula seems not to have been proposed yet.

    The purpose of this study is to clarify not only static but also dynamic ore pressures utilizing the distinct element method (DEM) that can simulate the behavior of individual ore particles. The calculation program considering the coupling effect of the ore particle's motion and the ship hull structure's deformation utilizing DEM and the finite element method (FEM) is developed.

    At first, an experiment using the scaled hold model was performed in order to examine the compaction behavior of ore under the repeated rolling motion. Secondly, the accuracy of calculation results by DEM was confirmed comparing with the ore pressure estimated from experimental results in both static and dynamic conditions. Finally, the ore pressure acting on the hold structure of actual ore bulk carrier was calculated under the condition of static and repeated rolling motion of ship utilizing the proposed calculation procedure.

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  • Yu Setoyama, Daisuke Yanagihara, Satoyuki Tanaka, Kimihiro Taniguchi
    2018 Volume 28 Pages 75-88
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Residual ultimate strength of stiffened panel including crack-like defects under longitudinal uni-axial thrust is investigated. A single transverse/longitudinal crack with different length and location is considered and is introduced into the continuous stiffened panel model. A shell finite element (FE) modeling is adopted and the crack is modeled as a displacement discontinuity in the FE model by introducing double nodes along the segment. A series computation of nonlinear FE analysis has been carried out employing LS-DYNA to examine the ultimate strength and influence of the cracks to the collapse behaviors. Three types of panel thickness and four sizes of longitudinal T-shaped stiffeners are assumed. The reduction characteristics of the ultimate strength and change of collapse behaviors are discussed through the nonlinear FE computations.

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  • Masayoshi Oka, Tomoki Takami, Chong Ma
    2018 Volume 28 Pages 89-97
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Improvement of the estimation accuracy of the wave load is necessary to realize a rational ship structure design. However, a rational method has not been established to determine the operation limit which influences the wave loads. In this study, in order to clarify the effects of the weather routing in North Atlantic, the sea state ship encountered is investigated by utilizing AIS data and wave data (Hindcast). In addition, the maximum wave load is estimated by using the Strip method for the container ships and the relationship between the vertical bending moment (VBM) and the maneuvering is confirmed. Based on Hindcast, in which the position of ships is not considered, the maximum value of the significant wave height in North Atlantic is about 16m. In contrast, the ship encountered wave height based on AIS is estimated about 13m. The wave load is reduced by about 15% due to the storm avoidance. A method is proposed to estimate the wave load with considering the actual ship speed and actual wave direction. It is confirmed that the maximum wave load estimated by the proposed method is smaller about 27% than the long-term prediction value which assumed a constant ship speed (75% of the service speed) and uniform distribution of wave direction.

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  • Daisuke Shiomitsu, Naruyoshi Izumi, Kimihiro Toh, Daisuke Yanagihara, ...
    2018 Volume 28 Pages 99-110
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Ring-stiffened cylindrical shells are used in offshore and submergible structures which are exposed to the external pressure. There are two cases where the ring stiffener is attached inside or outside to the cylindrical shell. At the stage of initial design, several formulas have been used to estimate the shell buckling strength and the overall buckling strength of ring-stiffened cylindrical shells. However, as for the overall buckling strength, these formulas give smaller buckling strength of the inside ring-stiffened cylindrical shell and larger buckling strength of the outside ring-stiffened cylindrical shell than the calculation result obtained by FE analysis. In this paper, a new formula for estimating the elastic overall buckling strength of ring-stiffened cylindrical shells is derived and proposed based on the equilibrium of the circumferential force and the moment considering the change of the circumferential bending rigidity due to the effect of the curved member as well as the shearing deformation. Moreover, the accuracy of the proposed formula is verified by comparing with the calculation results by FE analysis.

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  • Tomoki Takami, Kazuhiro Iijima
    2018 Volume 28 Pages 111-120
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Estimations of extreme wave conditions and corresponding maximal structural responses are of particular importance for the sake of ensuring structural safety of ships. The present paper is concerned with developing a method to predict the extreme value of structural response at the double bottom structure accounting for the double bottom bending moment by using FORM and the coupled CFD and FEA. The FORM and so-called Model-correction-factor approaches are adopted. The nonlinear strip method is used for predicting a design point (predictor) under the designated limit state function, then the CFD and FEA coupling method is used for correcting the predicted design point (corrector). Two types of limit state functions are used in estimating longitudinal stress level at the outer bottom surface in order to investigate the double bottom bending effect. The discussion is made in terms of identified critical wave episodes (design irregular waves) and associated structural responses. It turned out that the presented approach is valid for identifying the design irregular wave and corresponding reliability index where the structural response of the double bottom structure takes an extreme value.

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  • Hidetaka Houtani, Yusuke Komoriyama, Sadaoki Matsui, Masayoshi Oka, Hi ...
    2018 Volume 28 Pages 121-132
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    This paper proposes a design strategy of a hydro-structural model considering the vertical-bending and torsional vibration mode shapes. A ship with large opening decks, such as a container ship, has its shear center below its bottom hull. In the proposed design strategy, such a shear center location is achieved for a ship model by imparting appropriate stiffness to its hull.

    We built a box-shaped model, whose length was 2 m, with urethane foam and polyethylene resin based on the proposed design strategy. A three-point bending test, a torsion test, and a decay test of the model were conducted to investigate its elastic properties. The vertical-bending and torsional moments were estimated from the strains measured with gauges based on the fiber Bragg grating (FBG) technology. The validation of the test results with finite element simulations revealed that the elastic responses were successfully measured using the model designed based on the proposed strategy with the FBG strain gauges.

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  • Masahiko Nakamura, Kenichi Asakawa, Tadahiro Hyakudome, Yasuhisa Ishih ...
    2018 Volume 28 Pages 133-144
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    A prototype of a 3000m-class underwater glider for virtual mooring is being developed by JAMSTEC (Japan Agency for Marine-Earth Science and Technology) with RIAM (Research Institute for Applied Mechanics) of Kyushu University. The vehicle houses observation equipment and glides back and forth between the sea surface and the seabed collecting ocean data in a specific area (virtual mooring area). The motions of the vehicle are controlled by moving its center of gravity using mounted weight-shifters.

    In the field experiments, although the vehicle is heeled by the weight-shifters, the phenomenon in which it did not turn was observed occasionally. Therefore, in this paper, its factor is examined by motion simulations. In the last part of the paper, the factor is verified by comparison of simulated results and field experimental results.

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  • Koji Gotoh, Tomoaki Utsunomiya, Masataka Nakagawa, Kazuki Yamane
    2018 Volume 28 Pages 145-154
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Floating wind turbine facilities, which are installed in the deep sea area, play an essential role to promote the green energy application. One of the problems associated with the commercialization of facilities installed in the deep sea is the reduction of the maintenance cost of mooring chain. Therefore, it is necessary to establish a quantitative wear evaluation method for mooring chains. Specific wear is one of the essential physical parameter to evaluate the wear performance of metals. However, detailed investigation of the specific wear of the mooring chain has not been performed yet. The pin-on-disk wear tests were performed to measure the specific wear in the air and in the substitute ocean water. As a result of experiments, it has been confirmed that the specific wear in the substitute ocean water was remarkably smaller than in the air, and the wear state was stable.

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  • Kouki Miki, Shigeru Tabeta, Katsunori Mizuno
    2018 Volume 28 Pages 155-161
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Fish behavioral models can be a beneficial tool for appropriate fisheries management and environmental impact assessment of ocean development. Especially, modelling of fish migration which is affected by the surrounding environment would be crucial. In the present study, we implemented several migration models in fish behavioral simulations. For a grid-based model which calculates spatiotemporal changes of population in each grid, we introduced a repulsive type migration model in which fish can sense the environment at only the grid where it stays. We also developed individual-based models which calculates the temporal change of coordinates for each individual fish, with migration models of repulsive and attracting type. The developed models are applied to fish behavioral simulations in Ise Bay, to investigate the characteristics of the models.

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  • Mitsuru Kobayashi
    2018 Volume 28 Pages 163-169
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Ship Drift Estimation has been widely used for weather routing navigation. Improvement of accuracy of the estimation makes energy-saving navigation more efficient. Ocean current estimation database, which is being used as ship drift speed in weather routing services, is generated by solving ocean dynamic models and by being assimilated with the satellite observation data. However, there are some differences between estimated current speed and ship drift speed which can be calculated from GPS, Log speed, Gyrocompass measurement values. This study proposes the method for ship drift estimation by means of ships' navigation data collected using AIS. In this results, the estimation error was decreased to 79% of that of ocean current estimation (JCOPE-T) in Kuroshio watershed area.

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  • Yue Han, Junji Sawamura
    2018 Volume 28 Pages 171-180
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    A numerical model is introduced to investigate both global and local ice-induced loads on ship hulls in first-year ridged ice fields. Probabilistic ice fields are generated according to the statistical distributions of ridge height and spacing. Based on a semi-empirical method, the cycles of contact, crushing, and bending constitute continuous icebreaking processes by which a numerical model of ship–ice interaction in level ice and consolidated layer in ice ridges can be developed. The ridge keel is regarded as a floating, homogeneous and isotropic granular solid. Keel resistance can be predicted based on ideas borrowed from soil mechanics: the bow component is calculated as an integral of resistance per unit width with a modified Rankine’s plasticity model, including consideration of the effect of ship movement and inertia force of ice accumulation in front of ship bow. The computation in this simulation is time-saving compared to DEM model used to simulate ship and ridge keel interaction in recent years. The numerical global and local ice loads are discussed through results of a case study conducted in a series of different ice conditions. Ship performance and statistics of ice-induced frame loads are analyzed. Comparisons are made of the simulated results against published results of model tests and field measurements in ridged ice fields.

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  • Shinnosuke Wanaka, Kazuo Hiekata, Taiga Mitsuyuki, Hiroyuki Yamato
    2018 Volume 28 Pages 181-188
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    In this paper, an integrated design database for management of ships' hull information, towing tank test results, and CFD simulation results is developed to support researchers who study to improve CFD technology using tank test and CFD data. To be more concrete, this paper proposes data scheme and develop database system to manage tank test and CFD data by applying metadata description with RDF(Resource description framework), which is usually used for Linked Data. As for the evaluation of the functionalities, the developed management system was applied to management of tank test and CFD data conducted in the University of Tokyo, and it was demonstrated that the data management by metadata can reduce the labor which is required for searching some data. Moreover, by utilizing a system analysis method, it is shown that the developed system's configuration is one of the Pareto optimal configurations under a specific usage context.

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  • Kohei Matsuo, Shuhei Fujimoto, Michio Shimada
    2018 Volume 28 Pages 189-201
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    In order to improve sheet metal forming work in shipbuilding, this paper focuses on press working, and introduces R&D on a system that outputs detail guidance information for press working based on geometry theory. The system outputs a guidance line of press working on a plate and an ideal target shape after press working. This allows workers to proceed according to guidance lines by using the conventional press machine. The validity of the proposed algorithm is confirmed in numerical simulation in this paper.

    This paper consists of 7 chapters. Chapter 1 is an introduction to explain the background and the purpose of this research as well as the composition of this paper. Chapter 2 reviews related works on sheet metal forming work in shipbuilding, especially on press working. Chapter 3 outlines a theory of lines of curvature. Chapters 4 and 5 are main subjects of this paper. Chapter 4 describes an algorithm for finding an accurate guidance line of press working based on lines of curvature. Chapter 5 introduces the development of a system which implements the above algorithm. In Chapter 6, simulation of press working by a FE method is carried out to confirm the validity of the proposed method. Chapter 7 is a summary of the paper.

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  • Sadaoki Matsui, Chikahisa Murakami
    2018 Volume 28 Pages 203-209
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    In general, the roll inertia moment and its longitudinal distribution etc. are not calculated strictly in wave load analysis but are calculated approximately by simplified formula, even though the detailed model is used in structural analysis. Needless to say, it is very important to correctly estimate the mass and the inertia moment of the ship for the motion performance as well as ship structural safety. In this paper, the authors proposed the practical calculation method which could obtain the mass, COG (center of gravity), the inertia moment of the granular/liquid cargo, and these longitudinal distribution from FEM model. Additionally, the comparison of roll inertia moment between the values from proposed method and the classical simplified formula for the ore carrier was conducted. Moreover, the longitudinal distribution of the roll inertia moment and the height of COG were calculated strictly and the influence on the torsional moment in waves was examined. The proposed method can be performed easily, which needs FEM model of a ship and the cargo shape which are normally prepared when direct load structural analysis is conducted.

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  • Koji Matsuoka, Masahiko Nakamura, Hiroshi Nishi, Sunao Mochizuki
    2018 Volume 28 Pages 211-223
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    Plesiosauria is a group of oceanic reptiles which disappeared at the end of Cretaceous. Currently, only fossils argues their existence. The purpose of this paper is to disclose gliding performance of the extinct Plesiosauria. The authors applied fluid engineering approach to this goal. In other words, we described motion as motion equation, performed computational fluid dynamics calculation to obtain hydrodynamic coefficients, and conducted motion simulation to solve our problem. Two models with different neck length, the one with longer neck and the other with shorter neck, were prepared to compare their performance. In our motion simulation, two models showed maneuverability depending on length of neck. This result suggests that Plesiosauria with different neck length behaved accordingly to the length of their neck.

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  • Norio Kondo, Yuki Tanaka
    2018 Volume 28 Pages 225-234
    Published: 2018
    Released: March 07, 2019
    JOURNALS FREE ACCESS

    We, in this paper, present numerical results of flow-induced vibration for collision of two side-by-side circular cylinders which are mounted with the damper-spring systems. Two side-by-side circular cylinders are arranged at narrow spacing in the smooth flow. When the spacing is narrow, it is well-known from the experimental data that the flow behind stationary two circular cylinders becomes the gap flow. Then the two circular cylinders move along flow to the in-line and cross-flow directions in the complicated gap flow. In our simulation, the Scruton number of the circular cylinders is given as 1.0 and the Reynolds number is 20,000

    .
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