Due to the increase of maritime transportation volume day by day it is necessary to design a ship hull having large carrying capacity with low resistance. For this purpose, the authors propose innovative concepts of Ultra Large Block coefficient Ship (ULBS). In this paper, its concepts and study plans are shown, and its bow wave breaking phenomena are investigated as one of the fundamental studies on ULBS hull form. As experimental studies, wave breaking surface areas caused by ULBS models are measured. As theoretical ones, wave making resistance coefficients and distributions of free surface elevation are evaluated by means of Rankine source method, and distributions of free surface disturbance function D(x,y) are evaluated by means of Baba's low speed theory. Various parameters related to the wave breaking phenomena are investigated in comparisons between experimental and theoretical results. Under these investigations, it can be concluded that theoretical results based on wave making resistance coefficients, surface integrals of the square of free surface elevation and surface integrals of the square of free surface disturbance function have strong elations to wave breaking surface areas.

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A novel ship concept which is called ULBS (Ultra Large Block coefficient ship) to reduce CO2 emission form sea transportation is under investigation at Yokohama National University. Since ULBS is supposed to have a very blunt hull and use of various flow control devices are essential for better hydrodynamic performance, flow field analysis around a ship is crucial for a design of ULBS. Computational Fluid Dynamics (CFD) is expected to be an efficient design tool for unconventional hull forms such as ULBS. To investigate the flow characteristics of ULBS, free surface viscous flows around the ship with and without a stern tunnel are computed. Total resistance coefficients are compared with each other and with experimental data. Grid convergence study is performed with respect to resistance for the verification of the results.The three dimensional vortical structures in the stern of the two hulls are analyzed and compared with each other. Large scale flow separations behind the stern due to the bluntness of a hull and effects of a stern tunnel to flow fields are discussed.

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The simple body-force distribution model by quasi-steady blade element theory is coupled with the Reynolds averaged Navier-Stokes (RANS) code CFDSHIP-IOWA to study the propeller-hull interaction. The ship model is Series S60 (C_B = 0.6) ship model without hub, without rudder and the propeller is a right-handed 5 blade fixed pitch Modified-AU methodical series type which is treated as infinite bladed model. Computations are performed for the ship sailing straight ahead with- and without propeller. In the without propeller case, the bare-hull results are made sure for confirmation with the experimental data to prove the magnitude of the flow field quantities with fair agreement. The computations are performed while the propeller model is working on various propeller loadings and the results of propulsive performances and flow fields in the wake regions are compared with the EFD data.Summarizing the results, the present propeller model proves its capabilities on the studies of propeller-hull interaction with much less computational effort and verifies its possibility for the load varying case.

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This paper concerns results of model tests and full scale measurements of the propeller designed for inland ship (749 GT chemical tanker) aiming 3% increase of propulsive efficiency comparing with the present conventional propeller.Three concepts, namely (1)small blade area, (2)decrease of hub-vortex, and (3)consideration of ship wake distribution are applied for the propeller design. NHV (Non Hub-Vortex) propeller, of which the blade area was decreased by 20% from the conventional propeller, was designed and towing tank tests (propeller open test and self propulsion test) and cavitation tests (cavitation observation, paint erosion test, and fluctuating pulse measurement) were carried out with the conventional propeller and the SBA-NHV propeller (Small Blade Area NHV propeller). The model test results showed that the propulsive efficiency of SBA-NHV propeller is about 4% higher than that of the conventional propeller and the risk of cavitation erosion and the fluctuating pressure of both propellers are almost equivalent. Finally, sea trial of 749 GT chemical tanker was performed with the SBA-NHV propeller which was newly manufactured. Results of the sea trials and the service performance demonstrated about 4% deduction of engine output without any problem of the ship vibration and cavitation erosion after 15 months operation.

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The vessels with waterjet propulsion system increase with the rapid growth in numbers of high speed vessels. It has been increasing when waterjet vessels do towing work. However, the towing performance of waterjet vessels has not been researched clearly.The purpose of this study is to investigate the towing performance of waterjet vessels. Bollard pull test and 2 ways towing tests which are towing ahead and astern were carried out by using the patrol vessels with waterjet of Japan Coast Guard. In general, a standard tow force of propeller vessels is 1.0tf/100PS. However, it was found from the test results that tow force of waterjet vessels is almost half of propeller's one. The cause of drop of towing performance for waterjet is the flow separations at the inlet's lip part.Since the numbers of impeller rotations becomes high to the low ship speed during bollard pull and towing, and the inlet velocity ratio (IVR) which means the inlet velocity to the momentum velocity becomes 1.0 or more. Duct flow of flash type inlet on bollard pull and towing were computed by flow solver "SURF"developed by National Maritime Research Institute. On the basis of those computed results, the loss due to the waterjet duct and the head of propeller and waterjet were evaluated and were compared with the towing test data. Comparison of computed results with test data shows good agreement. The results indicate that towing performance of waterjet can be estimated by evaluating the loss due to the waterjet duct.

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This study aims at the safe navigation of a ship moving in the proximity of the bank under steady wind pressure. A directional stability criterion is presented for ships moving in a channel taking the wind effect into account. The wind effect on the check helm required for course keeping in the channel and the directional stability is investigated using the new criterion for a container ship with 136.7 m in length moving in the channel where the representative width is 89 m. The check helm angle reaches to 15 deg in wind velocity 9.6 m/s and wind direction 90 deg at low tide. Then, 9.6 m/s becomes the limiting wind velocity if the limiting rudder angle is assumed to be 15 deg. On the other hand, the wind effect on the directional stability is small. The studied container ship can navigate safely in the channel under the wind velocity which is smaller than 9.6 m/s.

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Recently, R&D of marine renewable energy becomes very popular all over the world. In this paper, a twin-type turbine is adopted as an ocean current power generator. The twin turbine system is theoretically torque free, since the left blade counters the right blade torque. Therefore, a floating body with a single point mooring concept can be used as a support of twin turbines. A computer code, which represents motions of the twin type current turbine with 6 degrees of freedom together with the non-linear mooring effect, is developed. The numerical code simulates fully coupled motions of the main body, two turbines and two mooring lines. The numerical results are validated with experiment in which a newly developed small size turbine ?generator model is used.The results show that the numerical results are in good agreement with the experimental results. Some numerical and experimental results show that the current turbine is stably moored even when the flow speed or direction is suddenly changed. The weather vane function of the mooring system is also demonstrated in the experiment.

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This paper proposes the methods of structural assessment of Arctic and sub-Arctic LNG carrier with different extreme ice load scenarios. First, iceberg (bergy bit) collision at midship and shoulder part in forward region are investigated assuming a normal or lower ice class LNG carrier. The shoulder part collision case, which is considered more critical, is analyzed with estimated absorbed energy from an actual damage record. Second, global strength in ramming operation of an ice breaking LNG carrier is investigated using a whole ship FE Model combined with global shear force. Finally, numerical simulations with special types of elements are carried out to take into account the ice crushing behavior.The authors conclude that, the proposed methods are very useful for strength assessment of ship in Arctic and sub-Arctic region,and spherical type LNG carriers are suitable to the concerned regions.

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The non-destructive testing for detecting structural damage at the earliest possible stage is significant in the safe and long life operation of large marine structure such as ships. In the non-destructive testing, the variation in structural characteristics from the original one to the damaged one is used to identify the damage. Vibration characteristic is one of the most popular criteria used for it due to its sensitivity for the structural damage. In this paper, a damage identification method used in non-destructive testing is proposed based on topology optimization focusing on the difference of eigenfrequency between the original structure and the damaged one. Eigenfrequency analysis of a structure is considered. A inimization of the least squared error between the eigenfrequency of the damaged structure and the target eigenfrequency is set as an objective function. An optimization algorithm is constructed based on the topology optimization and the method of moving asymptotes (MMA). The validity and the usefulness of the proposed method is confirmed by several numerical examples.

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Rotor-floater-mooring coupled response analysis is essentially important for design of Rotor Nacelle Assembly (RNA) and floating support structure of Floating Offshore Wind Turbine (FOWT). The authors have developed an analysis code UTWind for the analysis of the coupled response. Blades and floater are modeled as frame structure with beam elements. Lumped mass model is use for mooring. Aerodynamic load on blade is calculated by Blade Element Momentum Theory (BEM), and hydrodynamic load is calculated by Hooft's method, and Morison equation was modified to be applicable to cylindrical element with cross section with two axes of line symmetry. The equations of motion of rotor, floater and mooring are solved in time domain by weak coupling algorithm.The numerical results by the code were compared with experimental results in wave and wind-wave coexisting condition with/without blade pitch control and showed good agreement. Response by negative damping was reproduced by the code and showed good agreement with experiments.

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In this study, as an alternative to uniform corrosion model, the surface geometry of the corroded plate is represented by the random field model (Karhunen-Loeve Expansion Method). Capability of the random field model to represent the random properties of corroded surfaces is studied. The random characteristics of the real corroded surface are investigated based on the measurement data of the real corroded specimen. The random characteristics of minimum cross sectional area of the generated plates with random field corrosion are estimated by PCE (Polynomial Chaos Expansion) method as well as Montecarlo simulation to evaluate the availability of PCE to estimate stochastic properties of strength of corroded plate. By using PCE, the numbers of samples can be reduced significantly to get the accurate results and this effect is favorable to time consuming analysis. Finally, the ultimate tensile strength of the plates with random field of corrosion is obtained by non-linear three dimensional finite element analyses (FEA).Based on FEA results, random properties of the ultimate tensile strength of the plates are obtained using PCE.

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Fatigue crack propagation under biaxial tensile loading containing phase differences is highlighted in this study. Ships and offshore structures are subjected to many types of loading, e.g. wave induced forces, gravity, and inertia forces. Generally, these loadings have different axial components with different phases. However, the structural integrities of structures and vessels are evaluated according to design codes based on theoretical and experimental investigations under a uniaxial loading condition. Most of these codes are based on the S-N curves approach. An approach that does not use S-N curves has been favored by researchers, with the fracture mechanics approach preferred for evaluating the fatigue life of structures. An advanced fracture mechanics approach was developed based on the Re-tensile Plastic zone Generating (RPG) stress criterion for fatigue crack propagation. In this study, fatigue crack propagation tests under biaxial loading with four different phase conditions and two different loading components are performed and the effect of the phase difference under biaxial loading is evaluated. We present a numerical simulation method of fatigue crack propagation based on the RPG stress criterion under different biaxial loading phase conditions and the validity of our proposed method is confirmed by comparing the estimated fatigue crack propagation histories with measured data.

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Most all of the thermal power plants in Japan are located on the shore and use seawater for cooling the turbine steam. The discharge of heated seawater should be restricted not to affect on the coastal ecosystem, and in addition, the seasonal variation of temperature of intake seawater is recognized as the significant factor of the power generating efficiency. One of the authors et al proposed a new cooling water system so as to avoid such problems, that is, the cooling water would be contained in a closed circuit pipe system and circulated between cold regions of the deep water and the condenser for turbine steam cooling. Fouling on surface of the heat exchanger may cause the degradation of heat exchanging performance. It is known that there is a quite small chance in the dark and clean deep sea water to produce the fouling, but we have not so many knowledge in case that the temperature is high at the circumstances in deep water. herefore,the effect of temperature on the fouling on the heat transfer surface is experimentally investigated in this study. A slender titanium pipe is immersed in the actual deep sea water btained with the deep water intake facilities in Ohshima Island, off the Izu Peninsula, and held in a container keeping 10 degC in temperature and darkness without light. Heated water at 80 degC is continuously put into the pipe and the decline of temperature along the pipe and the situations of the surface of pipe are observed for 30 days. As a result, bio-fouling, a thin bacteria film is observed on the heat transfer surface when the temperature is higher than about 40 degC.

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Side-scan and forward looking sonars are some of the most widely used imaging systems for obtaining large scale images of a seafloor, and their use continues to expand rapidly with their increasing deployment on Autonomous Underwater Vehicles. However,it is difficult to extract quantitative information from the images generated from these processes, in particular, for the detection and extraction of information on the objects within these images. We propose in this paper an algorithm for automatic detection of underwater objects in side-scan images based on machine learning employing adaptive boosting. Experimental results show that the method produces consistent maps of a seafloor.

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Ecosystem including human beings owes its life activity to material cycle in earth system. With regard to industrial world,human beings extract materials from material cycle and change them into available material and energy by chemical reaction. As a result, they exhausted a lot of materials to the environment and thus recent environmental crisis occur. With regard to coastal area,which is strongly effected by human activities, it faces serious environmental problems such as red tide and green tide. To overcome these problems, it is very important to prompt material circulation between land and sea. In this paper, we propose exergy-based approach to evaluate sustainability of material cycle system. We verify proposed approach with a simple material cycle system. The results indicate that exergy can be a useful indicator for the evaluation of the sustainability of material cycle system.

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Extreme value estimation, such as maximum wave height estimation, is critical for robust and cost efficient design of ocean structure. Some previous methods are incapable of quantifying the confidence interval when taking variance of shape parameter into account. We propose a new method based on likelihood. The utilization of group likelihood, profile likelihood and deviation method permits the use of likelihood inference for extreme value estimation, even when the distribution is non-regular. We conducted a Monte Carlo experiment to show the performance of this new method for 3 parameter Weibull distribution. We also revealed the problems with Goda's estimation method. Our robust results suggest the use of likelihood inference to quantify the statistical uncertainty and the asymmetric distribution of confidence intervals, which have been overlooked in previous studies.

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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 an observation equipment and glides back and forth between the sea surface and the seabed collecting ocean data in a specific area (virtual mooring area) for more than one year.This paper summarizes the design concept and an outline of the glider and shows the results of the gliding tests in a towing tank.

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In recent years it has become evident that ocean data in time and space is required to make predictions of environmental changes on earth. As one method of acquiring data, we propose a virtual mooring system using an underwater vehicle, and have developed a test-bed vehicle called "BOOMERANG" which can glide back and forth between the sea surface and the seabed collecting ocean data.Since the results of field experiment in March 2010 were satisfactory, construction on a prototype vehicle for practical use was begun in April 2010. In order to improve reliability and to enable prolonged use, the performance of various pieces of loading pparatus of the vehicle was improved. This paper presents details of the construction of the prototype vehicle for practical use and results of the field experiment.

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It is inevitable to maintain the safety and efficiency in the maritime transportation. Especially, the steep rise of crude oil price requires shipping companies to minimize fuel consumption more than ever. Weather routing services are focused on shipping companies with international transportation. However, there are still many problems on accuracies of current models, such as sea forecasts or slow down due to ship motions. It is the reason why those continuous databases, for examples, ship motions, navigation or engine parameters, or sea conditions, are not enough accumulated to develop weather routing models. In this study, those databases have been observed for a couple of years in a 20,000DWT class bulk carrier in worldwide voyages. Some new relations can be known about ship motions, slow down, or wave conditions. The verification of ship motions and waves is carried out here with observed databases and numerical simulations of frequency response of ship motions and that of weather and oceanography. Finally, some points are discussed to construct the new methodology of total evaluation of international maritime transportation in the future.

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Modal shift has a lot of merits in environmental and transport safety aspects, but it does not seem that it spreads enough in cargo transportation in Japan. To get effective policies for promoting it, the transportation simulator which can estimate quantitative effect of transportation system change is useful. In this paper, we develop cargo flow simulator by using disaggregate nested logit model to analyze changes by effects of policies and economic situation. The simulator we develop is a detailed one in which whole country is divided into 207 livelihood spheres, 7x2 patterns of carriage modes are considered and whole inter-domestic cargo flows are treated for each class of articles. It has enough reproducibility, and with the simulator we estimate the effect of cargo lot size and modal shift potential besides lead time and transport cost on ton-kilo basis to get basic guiding principles for achieving further modal shift.

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Most all of the thermal power plants in Japan are located on the shore and use seawater for cooling the turbine steam. The discharge of heated seawater should be restricted not to affect on the coastal ecosystem, and in addition, the seasonal variation of temperature of intake seawater is recognized as the gnificant factor of the power generating efficiency. In this study, a new ooling water system is proposed so as to avoid such problems, that is, the cooling water would be contained in a closed circuit pipe system and circulated between cold regions of the deep water and the condenser for turbine steam cooling. The general concept of the proposed system is presented and its characteristics compared with the conventional ones are discussed, and then, the effects on power generating efficiency with use of deep sea low temperature and drag reducing additives to the circulated cooling water are examined.

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3D CAD systems are mostly used for ship design in shipbuilding industries today. However there is very limited focus on ship design automation. Recently, ship design automation became an emerging trend in global shipbuilding industry. This paper will introduce rule based ship design automation techniques using 3D CAD system. Authors will first introduce the design automation achievements, then the detailed analysis of automation problems faced during the automation implementation and finally the research study will prove how the design automation problems are resolved using the Petri nets graph theory automation concepts invented by the authors. This theory will help shipyards to increase the quality of their production, reduce the design time and increase their reliability on rule based design automation. The Paper will conclude with the possibilities of the future work using Petri nets theory.

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In the ship-hull design phase, the distance of longitudinal discontinuity is enlarged, by up to 100 mm for example, until its effect is thought to be minimized. To control tolerance, we used a technique to estimate the coefficient of the misalignment effect: the ratio of the stress with misalignment to the stress without misalignment. Current methods, created using Strength-of-Materials misalignment model, cannot be applied in the design phase. Longitudinal discontinuity models are needed, as there have been no studies of these joints and it is impractical to do finite element (FE) analysis in each case. We propose an estimation method of the coefficient of discontinuity effect in cruciform welded joint with shell plate. First, we created a new equation to estimate the coefficient in Strength-of-Materials model. Second, we found the membrane component of a discontinuous member stress is reduced because of the shell plate and the coefficient converges given a certain discontinuity value. Third, a modified equation taking the effect into account indicates the coefficient in the joint with shell plate.

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