With the recent rapid progress of high-end computers, i.e., one million times faster than it was twenty years ago, it is expected that applications of fully-resolved large eddy simulation (LES) which directly computes the streamwise vortices in a turbulent boundary layer will become feasible in many engineering fields within a few years. The objective of this study is to investigate feasibility of applying fully-resolved LES to the prediction of model ship hydrodynamics. For this purpose, bare hull double model computations of KVLCC2 are carried out with one billion computational grids by using 1,536 computing cores. Feasible results are obtained at two different Reynolds numbers. Details of the turbulent boundary layer and the wake stemming from them are simulated well. Since the boundary layer is not tripped in the computations at Reynolds number of one million, laminar-turbulent transition and laminar effects are observed in detail by instantaneous vorticity distributions and the local skin friction coefficients.

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The single-propeller/twin-rudder system composed of single propeller and two high-lift rudders of fish-tail type has been installed on many vessels in Japan. With this system, a ship can be maneuvered at any mode including going astern, hovering, dead slow forwarding and turning by means of various rudder angle combination, with propeller revolution being kept in the forward direction. To improve propulsive efficiency of the single-propeller/twin-rudder system, a pair of reaction fins is attached between two rudders where the propeller slip stream passes. Form, size and setting angle of the fin affect propulsive performance a great deal.A method to determine of the setting angle of fin is discussed in this paper. Fundamentally the setting angle is determined by doing model experiment in model basin. As the second method we propose to estimate the setting angle based on fluid pattern of stern. A concept of the datum line for evaluation of lift of fin is introduced. A method to determine the repres ntative inflow angle to the fin by the datum line and to determine the optimum setting angle of fin is discussed.

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The added resistance in waves is one of the important factors for the evaluation of the ship performance in actual seas. As the added resistance in waves is associated with the bow shape above the waterline as well as that below the waterline, the relation between them has been studied, and the bow shapes to reduce the added resistance in waves have been developed and installed to the actual ship. In this paper, the development of the energy saving device STEP that reduces the added resistance in waves due to the wave reflection is described. The optimal shape and the optimal position of STEP were investigated for the 170 meters long pure car and truck carrier in 3 meters height of head waves as the design condition. Through the model tests, STEP has indicated 18% reduction of the added resistance in waves in the design condition. In addition, the effect of STEP under the off-design conditions has been also examined. From the calculation of the ship performance in actual seas, the reduction amount of CO₂ emission from the ship has been evaluated as 2% in head waves and winds of Beaufort scale 6.

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Tidal current power generation is attracting more and more attention these days for its cleanliness, predictability and reliability.A brimmed diffuser from wind-lens technology is tested in this study in order to observe its effect on power generation efficiency in tidal current turbine systems. Validation experiments were carried out in the circulating water channel for the bare turbine and the shrouded turbine, results of which proved that the diffuser improved the performance of the tidal turbine. The computational fluid dynamics (CFD) method and the blade element momentum (BEM) theory were used to evaluate the performance of the bare turbine and the shrouded turbine. For tip speed ratios (TSRs) of 2.5 to 4.0, both CFD and BEM calculations for the bare turbine were well-correlated with the experimental data. For the shrouded turbine, CFD results failed to exactly reproduce the experimental results with the turbulence model and mesh size utilized, but BEM results did succeed with TSRs greater than 3.0. Considering correlation with experimental data and calculation time cost, BEM is a satisfactory method for evaluating the performance of a tidal current turbine.

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The Actual Sea Model Basin was completed at August, 2010 at National Maritime Research Institute, Japan. The basin is equipped with wave generators surrounding the basin, towing carriage and wind blowers in which actual sea conditions are realized. Using the basin verification on the resistance test in waves was carried out. Comparison with the added resistance in waves is carried out between the other tanks in our institute using models of a container carrier and a bulk carrier. Through the evaluation of the decrease of ship speed, it is confirmed the deviation is smaller than that carried out the cooperative tank tests previously using the same ship form among the other tank institutes in Japan. Here the result of the verification is reported.

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Concern for safety, phenomenon of a slack towline on tow-towed ships during maneuvering is important subject to be studied. This paper is aimed at clarifying a mechanism of slack towline, which comes into derivation of slack towline criteria.By applying the steady turning theory of tow and towed ships presented by Fitriadhy et al (2011)³⁾, a simple formula was proposed for appearance limit of slack towline during turning. The formula can explain the slack towline criteria on the towing cable length, turning radius of the tug, size of the towed ship, relation with the course stability of the towed ship and so on. For the validation of the formula, it was compared with results by the tank test and nonlinear time domain maneuvering motion calculation for tow and towed ships. The theoretical tendency of the slack towline appearance limit is qualitatively agreed with the results by the tank test and nonlinear calculation. The present formula is useful for a better understanding of the mechanism of slack towline during turning.

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To utilize floating structure under heavy environmental condition in sea safely, motions of the floating body and the mooring forces acting on the body have to be reduced. To decrease these motions and mooring forces, fins attached structure has been proposed.In this paper, as a first step of the study, two vortex methods, the Random-Walk method and the Core-Spreading method, are applied to uniform flow past a circular cylinder and heaving fin plate under free surface. In the simulation of uniform flow, we conduct parametric study which helped us determine the numerical parameters to be used in subsequent simulations. Then, the simulated wake velocities are compared with experimental results to verify the calculation accuracy. In the simulation of heaving plate, hydrodynamic forces on the plate are simulated and compared with experimental results.

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Nowadays the larger tanker ships sometimes face the difficulty to access the port inside since the infrastructure such as water depth, berth length and port area is not suitable for the ship size. Ship-to-Ship (STS) transfer either offshore or inshore could be helpful for that problem, which is known as a lightering operation. In the stage of berthing, the larger ship maintains the steerage on a constant heading, and the smaller ship maneuvers alongside. On completion of mooring, a cargo transfer starts while two ships are underway, anchored or drifting. Although STS operation might be established, two ships in close proximity have high potential collision risks so the hydrodynamic force characteristics including the interaction among hulls and rudders should be more examined.In this study, those characteristics between two Wigley parabolic hulls were investigated experimentally and numerically. Captive model tests were conducted to measure the hydrodynamic forces acting on two hulls and two rudders, changing lateral and longitudinal distance between ships, hull drift angle and rudder angle. The experimental results were compared with numerical analysis using a nonlinear lifting body theory. We found that when a ship steered, the circulation was induced to the other ship hull due to the interaction. It results in causing the additional lateral force and moment. When a ship is in oblique towing, we see the other ship hull suffers from the interaction force and moment and they change complexly depending on the hull drift angle. Those interactions become stronger as two ships become closer. The lifting-body based calculation method can capture such hydrodynamic force characteristics between two ships with a rudder.

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Amendment of MARPOL Annex VI is adopted at International Maritime Organization at 2011 and it enters into force from January of 2013. We are requested the measures for the reduction of greenhouse gas emission from ships. For that purpose estimation of the fuel consumption of the engine in ship operating condition with accuracy becomes important.In operation ships encounter winds and waves. As for the engine, the operating conditions are changing by the disturbances in actual seas.In this paper a calculation method of ship fuel consumption is proposed considering the engine operation modes. The considered modes are the revolution constant or the power constant. The calculation treats the limits of the engine operation. The limits are the torque, the over loading protection and the fuel index of the engine. If the engine operating point is over the limits, the engine controls the revolution to decrease. At the same time the ship speed decreases and the fuel consumption per hour also decreases. The relation between ship speed and fuel consumption is discussed here.

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Brittle fracture propagation issue has been focused from the viewpoint of margin of safety in some steel structures which require high fracture safety. In this study, Importance of absorption of fracture surface energy(G_c) during cleavage crack propagation in poly-crystal material is pointed out. Model experiment at -196 deg.C by Compact Crack Arrest specimen and FEM analyses based on the local stress criterion method were performed using YP32 steel and its material constant considering G_c concept. FEM analyses where the critical stress, σ_f is set to 2150MPa which is the same value as its critical stress for crack initiation and G_c is set to be 500J/m² show excellent agreement with experiment in their crack propagation velocity and arrested location.

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Authors investigate the fatigue crack propagation behavior of solid austenitic stainless steels SUS304L, SUS316L and SUS316LN in order to conduct the characteristics of fatigue behavior of each stainless steel. Not only the constant stress amplitude tests, but also the load decreasing tests called by ΔKth test regulated by ASTM E647 are performed to identify the material constants of fatigue crack propagation. Comparison of the fatigue crack growth behavior of SUS304L, SUS316L and SUS316LN with mild steels is also performed. Authors also investigate the fatigue life of load-carrying type cruciform joints of austenitic stainless steels,which are modeled upon the lower end of vertically corrugated bulkhead of chemical tankers. Besides, the possibility of quantitative numerical simulation of the fatigue crack propagation for the stainless steels is also investigated. This simulation procedure applies for the advanced effective stress intensity factor range based on a Re-tensile Plastic zone Generation (RPG) load and the fatigue crack closure phenomenon is quantitatively considered. The experimental results are compared with the numerical simulation results in this study and the validity of fatigue crack growth simulation procedure applied in this study is confirmed.

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In this paper, a series of water impact simulations is carried out by using fluid-structure interaction (FSI) function of the nonlinear dynamic structural analysis code LS-DYNA. Water impact phenomena of wedge shaped body and circular cylinder body are simulated in the present study. For the purpose of the validation of numerical simulations, the water impact pressure's peak values, pressure distributions and structural responses are compared with conventional theories and experimental results.A series of rigid wedges' water impact simulations is performed and water pressure values are compared with conventional Wagner's theory and experimental values. Then, a series of elastic cylinders' water impact simulations is performed and structural responses are compared with experimental values. It is found from the present study that water pressures and structural responses calculated by FSI analyses using some models are in good agreement with Wagner's theory and experimental results.

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A new model for dynamic crack propagation and arrest in steel plates is proposed. The model is based on the local fracture stress criterion and incorporates the influence of plastic deformation on the tip of a dynamically propagating crack. Under extremely high applied stress intensity factor, the crack-tip plastic zone develops so as to decrease plane strain condition region along the crack front.This leads to the relaxation of plastic constraint and the lowering tensile stress at the crack tip. It is thereby difficult for the crack to keep propagating. The proposed model is applied to the past published ultra-wide crack arrest tests, where a crack was arrested even if stress intensity factor K was higher than arrest toughness K_ca obtained by the standard crack arrest test. Although the results have been unexplained for many years, the numerical results of the proposed model show good agreement with the past test results. It is found out that the primary reason of the crack arrest of ultra-wide plate tests can be explained by the loss of plane strain condition at the crack front.

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It is necessary to make clear the effect of torsional moment on the ultimate strength of the ships' hull girder for the accurate assessment of that of ultra large container ships with large deck openings. In the present study, the extension of the simplified method of progressive collapse analysis based on Smith’s method is attempted to the case of combined loading condition. Firstly, progressive collapse tests are carried out on 1/13-scale three-hold hull girder models referring to a Post-Panamax container ship. The models are fixed to the rigid wall at the aft end and a couple of forces are applied to the fore end so as to generate torsional and vertical bending moment simultaneously. The progressive collapse tests are conducted for the case of the various combinations of torsional and bending moment. The nonlinear finite element analyses by LS-DYNA are executed in accordance with the test conditions. From the test and calculation results, the progressive collapse behavior and the ultimate strength of hull girder models under combined loading are examined. The results will be a basis for the verification of a new simplified analysis method which will be presented in the forthcoming reports.

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This paper discusses the influence of the rotation of the neutral axis on the residual hull girder strength of asymmetrically damaged ships under longitudinal bending. Progressive collapse analysis of the damaged cross section is performed applying the Smith's method for the biaxial bending problem. An explicit expression of the location of the neutral axis including its rotation is given as a function of biaxial curvatures. The procedures of the progressive collapse analysis of the cross section under biaxial bending are presented for several loading and constraining conditions. A series of progressive collapse analysis of bulk carriers and double-hull tankers having collision damages at the side structures is performed. The residual hull girder strength of damaged ships considering the rotation of the neutral axis is found to be reduced from that obtained by constraining the rotation. The reduction rate of the ultimate strength is investigated for different damage location and extent. For a sagging condition, simple formulae to estimate the residual strength and the reduction rate due to the rotation of the neutral axis are proposed using the elastic cross-sectional properties and critical member strength. The effectiveness of the formulae is examined through a comparison with the progressive collapse analysis. The proposed analysis method and formulae can be utilized for the rational assessment of the residual hull girder strength of damaged ships.

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The Strait of Malacca considered to be the busiest and is one of the world's most dangerous shipping lanes in the world because of its heavy traffic, narrowness, sharp turns, and many other critical factors. Therefore, maritime safety in the Strait of Malacca is an important issue. With a length of approximately 500 mi (800 km), the Strait of Malacca is the longest strait in the world used for international navigation. It forms the main seaway connecting the Indian Ocean with the China Sea and provides the shortest route for tankers shuttling between the Middle East and Asian countries. Therefore, this strait is the busiest shipping lane in the world. The principal aim of this study is to analyze the degree of safety in navigating the Strait of Malacca in terms of indices such as the danger score using the analytic hierarchy process (AHP) and the automatic identification system (AIS) data. The objectives of International Maritime Organization (IMO) of implementing the AIS are to enhance the safety and efficiency of navigation, safety of life at sea,and protection of maritime environment. In this study, the AIS is used as a source of data and AHP is used for evaluating the danger score, the sum of the weighting factors determined by this method, for the Strait of Malacca.

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It is considered that the weather and ocean such as the wind, the tidal current and the wave are the most important factors to a sailing ship. In this paper, the numerical calculation methods of the tidal current, the wind and the wave are proposed in the coastal sea area. In second, the numerical navigation system is investigated by the simulation. The purpose of this paper is to propose the numerical estimation methods of weather and ocean, and to discuss about the simulation of numerical navigation for a sailing ship under effects of numerical weather and ocean. The simulation of numerical navigation to a sailing ship is carried out under the effects of numerical weather and ocean. The proposed numerical navigation is very effective for the estimation of the ship position for a sailing ship. It was found that the numerical navigation system is possible to introduce to the weather routing system in the coastal sea region in future.

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The Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) on board of the Advanced Land Observing Satellite (ALOS) was launched for earth observation and there are more than 12 million scenes of archives including coastal areas during period of five years. Nowadays, the number of AIS (Automatic Identification System)-equipped ships is increasing for maritime safety and monitoring vessel traffic. The purpose of this paper is to acquire the knowledge about kinetic analysis of vessel traffic by satellite images with simultaneous acquisition of AIS data. We extracted vessel information from ALOS images with AIS data by using GIS (Geographic Information System) in the Straits of Malacca on 4th May 2010. It should be noted that this process would enable to classify various length vessels with AIS-equipped or AIS-unequipped. Then, Speed and Course of each vessel was obtained from observation time difference between two satellite images. The comparison between the information of each vessel from satellite images and AIS data (SOG:Speed over ground and COG:Course over ground) as actual measurement value show a quite good agreement.

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Recently, in the cargo transportation between international, the rate of the change to airlines from conventional container ships rises greatly (over 40% of money base in Asia) in the background of the increase of transit needs between international of the high-tech products such as the electronic parts, semiconductors, office supplies and, etc. In this reason, the transportation costs of the high-value-added commodity groups soar, the fare differences between aircrafts and conventional container ships become large, and the problem of the earth environment has become aggravated. From such circumstances, in order to control the rise of the rate of the change to airlines, the Very High Speed MRTH Full Container Ships applied the MRTH (Minimum Resistance Twin Hull) developed by Dr. Maruo¹⁾, should be adopted to achieve highly speeding up of the container transportations between international.The MRTH Container Ships can provide with an excellent high speed performance that breaks down the limit of the speed performance of conventional container ships and can make the difference at the lead time with aircrafts insignificant by cheap fares.In the present paper, the feasibility studies when the MRTH Container Ships are introduced into the coastal shipping routes, Japan-North West route and North East-Europe route, are described.

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Although many methods have been applied to solve the combinatorial optimization problem, there are many cases in which the global optimum solution cannot be gained within a practical computation time, even if computers become more advanced. Recently,ant colony optimization (ACO) has been proposed as a meta-heuristic method to solve this problem. ACO has been tried and verified for the traveling salesman problem (TSP) to obtain the shortest path among many routes between many cities, as a representative combinatorial optimization problem. The authors have applied ACO to ship production work, such as welding and cutting, and now "marking", which is a process of writing information required in the next stage of manufacture, such as fabrication or assembly, on a steel plate by flame spray coating using a numerical control (NC) machine. In this work, the problem of searching for the optimum pathway of the NC marking torch is discussed, and a method to obtain the optimal route in a short time is presented. A system for improving ACO was developed and successfully applied to the shipyard.

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Improvement effect of painting efficiency by using low volatile organic compounds (VOC) paint was investigated experimentally and numerically. We measured painting efficiency of low-VOC paint and conventional paint under crosswind by wind tunnel experiment. The painting efficiency and particle size distributions of spray of the test paints were calculated by simple numerical calculation. The efficiency of low-VOC paint was clearly better than that of conventional paint. It was shown that the motions of spray particle of the low-VOC paint were predictable by the simple numerical model.

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Diesel engines have been used as power sources of the propulsion as well as the electric generator for oceangoing vessels.Although they have advantages in the thermal efficiency and the durability compared to other types of internal combustion engines,their exhaust gases contain harmful substances, such as the nitrogen oxide, the sulfur oxide or the particulate matter, which cause the environmental pollutions. Dimethyl Ether (DME) has been paid attention as one of alternative fuels of the diesel engine, since it emits less soot emission compared to the fossil fuels. Thus, various studies have been done that use neat DME as the fuel oil of diesel engines. The aim of this study is to clarify whether liquefied DME mixed with Bunker C (JIS C heavy oil) could improve the engine performance of diesel engine. In the present study, a pressure resistant fuel tank was made to mix liquefied DME and Bunker C, and a direct injection type of diesel engine was used to analyze the combustion characteristics. From the experiments, it is obtained that the ignition delay can be shorten with mixing DME to Bunker C. Also, DME mixed fuel can reduce the incomplete combustion substances, such as the carbon monoxide, the unburnt hydrocarbons and the soot. Moreover, it can diminish the amount of the carbon dioxide emission with DME mixed fuel while keeping almost the same thermal efficiency with neat Bunker C.

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