Nowadays there are many kinds of distance measurement methods. For example, in the ocean engineering field, the distance can be measured by sensors using optical, electromagnetic waves or acoustic waves. GPS is becoming the popular method now. Of course those methods have their own merits and demerits. Here the distance is not horizontal or vertical distance between the target or obstacles but the longitudinal distance of a target from a observer or camera, and this will be said as "depth distance". Here, for the time varying depth measurement in tank experiments, we propose an alternative cheap and stand-alone optical method using continuous single calibrated optical images, combining the automatic tracking algorithm and depth distance estimation algorithm. The wave effect on measured mean depth distance time history of freely floating bodies can be eliminated by filters but the fluctuation by ship motions is an important information, so we try to carry out some simulation about this fluctuation. The main object of this paper is to describe the proposed algorithm used in the software development and the results obtained in the model experiments carried out in a towing tank to estimate the depth distance.

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There are abundant fisheries resources around the Japanese coast and the fishery is one of the important industries in Japan.When an accidental oil spill occurs on the sea, it is important to get the understanding and cooperation from the fishermen atdamaged area for the recovery of spilled oil. In order to treat spilled oil, the risk assessment from the viewpoint of fisheries damage is needed.The prediction model of fisheries damage due to oil pollution has been developed to predict a loss of catch at damaged areas on Geographic Information System (GIS). This model calculates the distribution of spilled oil and oil concentration, and predicts loss of catch at damaged areas where the oil concentration exceeds the effect concentration rate of marine organisms by using fisheries database. It should be noted that the oil concentration is the assessment index in this model. There had been no assessment method to predict the fisheries damage due to oil pollution using the model of oil spill movement and fate in Japan. Further, the fisheries damage due to actual oil spill accident at the Akashi Channel in March, 2008 is predicted to verify its validity by using this model. The comparison between the actual fisheries damage and estimated result gives a quite good agreement using the oil spill simulation model (OILMAP) which is widely used in the world.

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The present paper presents the development of an anti-fouling system for marine structures in consideration of marine environment.We produced anti-bacterial agent using silver ion. We conducted the experiment which checks whether the amount of adhesion of sessile organisms is proportional to the content of the anti-bacterial agent, in the port of a Japanese coast. From the result of the 40-Day experiment, it turned out that its amount is reduced by 80% from 40% regardless of the species of sessile organisms.

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The anxiety about the risk of international food shortages is getting larger in the face of population growth, climate change and other concerns. On the other hand, the efforts to examine marine resource utilization addressing food-supply issues, such as large-scale offshore fish farming, ocean fertilization, etc. are expected to increase. A preliminary study to assess the social and economic impacts of such technologies is thus an essential component of strategy and policies for ocean development. In the present study, a food economy model including marine products is applied to investigate the effect of ocean fertilization. The sensitivity of the model for the external scenarios such as population, GDP, and crop yield, are also examined. The results show that the prediction for the supply of fishery products, which will stay low level, be almost robust under those scenarios. It is indicated that increasing fisheries products could become an effective measure to improve the self-sufficiency of food in Japan. It is clarified that ocean fertilization will be effective when it is applied to the fish species whose stock abundance is small.

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The present paper describes the application of the moving particle semi-implicit method (MPS method) to a prediction of drifting distance and a collision force on a floating structure. Effectiveness of the application is verified.Calculation results of the MPS method are compared with solutions of the Stokes theory and corresponding experimental results in a wave tank. Solitary waves are applied to simulated tsunamis in numerical simulations and to the model experiment. A corresponding floating body is a pontoon type in this study. Tsunami propagation, the grounding on a wharf of the floating body,drifting of the floating body and a collision force of the floating body to a fixed wall is used to validation of the MPS method. From the comparison between the numerical simulation results and the experimental results, the applicability of the MPS method is discussed.

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This paper presents a calculation method for the unsteady cavitating propeller problem. The method is based on a simplified surface panel method "SQCM" which satisfies the Kutta condition easily. Hess and Smith type source panels are distributed on the propeller and cavity surface. Discrete vortices are distributed on the camber surface according to Lan's QCM (Quasi-Continuous vortex lattice Method). The boundary conditions to determine these singularities are the constant pressure condition on the cavity surface and the zero normal velocity condition on the propeller and camber surface. In the unsteady problem, we give the modified normal velocity instead of zero normal velocity at the end of camber surface in order to satisfy the Kutta condition exactly. The cavity shape in each radial section is determined so that the zero normal velocity condition is satisfied.In the present method, a cavity length for each radial section is given first. Then the singularities and the cavity shapes are determined.These steps are repeated until both constant pressure condition and normal velocity condition are satisfied on the cavity surface. Next, the cavity length is corrected in order that the opening at the cavity end will get closer to the target value. By using the corrected cavity length, the calculation is repeated from the beginning. These steps are repeated until the opening at the cavity end agrees with the target value in each section. In this method, constant pressure condition is satisfied including cross flow velocity because its effect is not small near the tip of a propeller blade.The variation of cavitation patterns, cavity shapes, cavity area and cavity volume in wake are calculated for two kinds of propellers. Good agreements are obtained between the calculated results and the experimental data.

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The objective of the present study is to elucidate the ow mechanism of delaying stall by use of wavy leading edges. Experiments were carried out to examine the effects of variant wavy leading edges attached on NACA0018 section wing of aspect ratio 1.6. The Reynolds number based on the chord length is Re_c = 1:38 × 10⁵ for the experiments. For these tests, lift, drag, and moment of wings with and without wavy leading edges were measured in a circular water channel. Flow visualization on the surface of wings was also conducted in order to clarify the eects of the wavy leading edges on the delaying stall. It is found that the wavy leading edges can control ow separation and delay stall, which in turn is good for producing large lift force at poststall angles of attack. Under the same height condition, the short width of wavy protuberance shows good performance of the wings compared with that of the long width. The wavy protuberance located near the wing tip does not enhance hydrodynamic performance.

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This paper is the first half of the experimental study on propeller characteristics in bubbly flow, and explains the test setup and the realized flow. A bubble generator was placed upstream of the propeller, and the nominal void ratio of the flow going into the propeller was varied between 0% and 5%. The distributions of the local void ratio and the velocity field at the propeller plane were measured using an optical probe and a five-hole Pitot tube, respectively. The measured mean void ratio at the propeller plane increased monotonically in proportion to an increase in airflow rate. The propeller open water test results at no bubble injection changed little by changing the towing speed and the propeller rotation speed. The flow field at the propeller plane was slightly retarded by placing the bubble generator. The bubble injection caused upward flow at the propeller plane due to buoyancy. The magnitude of the z-component of the flow (upward flow) increased in proportion to the average void ratio at the propeller disc,while the x- and y-components showed little change.

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The aim of this study is to clarify the characteristics of the Propeller Open water Test (POT) in bubbly flow. The part 1, i.e.the previous paper, has shown the experimental setup, conditions, the distributions of the local void ratio and flow field at the propeller disk. The part 2, i.e. this paper shows the POT results in the bubbly flow. The POT has been performed under several void fraction values between 0% and 5%. The wake effect due to the upstream bubble generator has been corrected using the thrust identity method. The thrust, torque, and efficiency of the propeller in bubbly flow become smaller than those without bubbles, and their reduction becomes larger as the void fraction in the propeller inflow increases. Tests using two different sizes of propellers have shown that the decrease in propeller efficiency due to bubbles is generally larger with the larger propeller. Tests at small pitch angle change have shown that the propeller efficiency reduction is small at the pitch angle change of ±1 degree, while that at the pitch angle change of ±2 degrees is greater, especially at large advance coefficients. A schematic diagram for the effects of air lubrication on both the ship and the propeller shows that, although the propeller efficiency slightly decreases due to the bubble inflow, the decrease in propeller load factor due to the decrease in ship's drag helps to recover the propeller efficiency.

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Reduction of green house gas from international shipping shall be put forward. For the reduction, it is important to promote to introduce ships of high energy efficiency to the shipping market. In actual seas a ship decreases her speed not only the deterioration and fouling effect but also by natural forces such as winds and waves. By design technique, ship propulsive performance in actual seas is able to improve. Hence ship propulsive performance in actual seas has much scope to improve the energy efficiency.We present a calculation method of decrease of ship speed in actual seas. From the point of accuracy, the method involves correction for added resistance in short waves combined with a tank test. As examples three kind of ship; a container ship, a car carrier and a bulk carrier are examined and the components of external forces acting on the ship are discussed.

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The present paper investigates a wind drag reduction mechanism generated by a square corner cut and a step shaped geometry in an accommodation house of ship. For this purpose, numerical simulations of turbulent flow around the simplified models of accommodation house are conducted by using Large-Eddy Simulations (LES). Comparing the drag reduction rates with wind tunnel measurements, the numerical results are validated. The numerical results show cavity flows in the square cut corner and the step, and they can reduce wind pressure acting on the front surface. The geometries also reduce separation regions around the accommodation house and enhance pressure recovery on the back surface. These results show a considerable contribution of the back pressure in the wind drag reduction. For more realistic condition, the interactions between the flows around a ship hull and an accommodation house are also investigated by LES with shiphull geometry. In the case at a yaw angle of 30 deg., the wind separates from the side edge of the shiphull and it does not impinge onto lower level of the accommodation house. In this case, the step shape is comparatively effective in the wind drag reduction and the back pressure has more contribution than the case without shiphull.

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Vortex induced vibration (VIV) responses of underwater line structures inclined against the normal of free-stream direction had been measured. Two 1440mm and 9500 mm in length circular section line structures with 12.7 mm diameter had been used. The VIV frequency of an inclined underwater line structure depends on the normal component of free-stream velocity because VIV is a vibration balancing the hydrodynamic force due to the vortex shedding and the restoring force and the hydrodynamic force by vortex shedding depends on the normal component of free-stream velocity. The tangential component of free-stream velocity has an effect on the VIV, too. When an underwater structure is set with an angle of inclination, an axial direction friction force comes out by the tangential velocity component. The structure inclination changes the natural frequency of the structure because the natural frequency of a line structure depends on the tension. The VIV response of an inclined underwater structure strongly depends on the normal velocity component. The VIV responses measured by accelerometers depend on the deduced velocity consisted of the normal component of flow velocity, 1st-order natural frequency of the structure and the structure diameter. The VIV responses of the underwater line structures were almost same as VIV responses of rigid circular cylinders excepting at the region occurring 2nd-mode resonance of the vortex shedding with the 2nd-order natural frequency. The natural frequency of a spring mounted mass system linearly depends on the order number. However, the natural frequency of a tensioned line structure is non-linear in the order number. The frequency of the In-Line VIV was about 2 times of the Cross-Flow VIV frequency, but the mode number of In-Line shape was not only 2 times of the Cross-Flow shape mode number. The shape mode depends on the relation between the VIV frequency and the natural frequency. The displacement of Cross-Flow VIV was about 4 times of the In-Line VIV displacement.However, bending stresses in the In-Line direction were almost same as the Cross-Flow direction bendi ng stresses, because themode number of In-Line shape was about 2 times of the Cross-Flow shape mode number.

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In recent years, a system to measure sea conditions in real time for carrying in a buoy is developed. In this system, wave conditions, those are wave height, period and direction, are obtained from calculating the buoy's motion equation with its accurate response operator functions using measured buoy's motion. Therefore, it is necessary to take the functions in design stage, in order to design for an optimum form of buoy for installed sea area. First, the accuracy of an existing motion calculation program based on potential theory is checked. It is found that the calculation overestimates the harmonic heaving amplitude for some buoy.Then, in order to understand the reasons, the characteristics of the hydrodynamic forces acting on buoy are investigated with a forced heaving motion test. From the flow observation around a buoy using visualization technique, large vortexes shedding under the body in the moment when buoy has maximum upward velocity are observed, and it is confirmed that viscous drag acts on buoy. Using a vertical cylinder model, the viscous drag coefficient acting on aft-body in the moment when the model has maximum upward velocity is measured by the forced heaving motion test for several KC numbers and 2D CFD calculation based on CIP method is also carried out, and the characteristics of the viscous drag are investigated and an empirical estimation formula is presented. Finally, a motion calculation including the viscous drag is carried out and the results are compared with measured results. It is confirmed that the calculated results are improved and shows good agreement with measured results.

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In this study, a roll motion estimation of fishing vessel with water on deck is investigated. Firstly, the characteristics of roll damping of a fishing vessel are investigated through the experiment. The Ikeda's method is modified for the improvement of accuracy of roll damping of a fishing vessel. Secondly, the effects of water on deck are investigated through the experiment. A database of hydrodynamic forces caused by water on deck is developed. In addition to the nonlinear calculation program of it based on shallow water theory is developed. Finally, roll motion of a fishing vessel with water on deck in beam sea is calculated. The results are compared with the measured results, and its validity is confirmed.

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In this paper, a statistical estimation procedure for parameters in an equation of ship's oscillation, such as a damping coefficient and a natural frequency, is proposed. It is important that a mariner grasps the performance of the ship, when carrying out safe operation of the ship. From a viewpoint of avoiding a resonance with a wave, it is especially important for the mariner to grasp the natural frequency of the ship. Using the procedure, the parameters can be estimated by using an observed data on board. Therefore,the mariner can always grasp the parameters of the ship under navigation.In this procedure, two kinds of stochastic techniques are adopted. The first one is a CAR (Continuous AutoRegressive) model that can gain precise parameters of ship's oscillating equation. In general, the ship motions in waves are regarded as a stochastic process.However, it has the problem that the noise process can not regard as a white noise. In the CAR model, it can be coped with by considering that the noise is an auto regressive process. The second one is a self-organizing state space modeling that can evaluate both the state estimation and the identification of unknown parameters in a general nonlinear non-Gaussian system. In this estimation calculation, Monte Carlo Filter which is a kind of Particle Filter is adopted. The goodness of the model is evaluated by using AIC (Akaike Information Criterion) with respect to the model.To examine the reliability of the proposed procedure, the numerical experiments are carried out by using the reproduced data under the condition which the unknown parameters are a fixed value. The estimated ship motion parameters based on the proposed method shows good agreement with the input data. Moreover, to examine the proposed procedure, the onboard experiments are carried out.Although some future problems became clear, we conclude that the proposed method is a powerful tool for the estimation of the ship motion parameters.

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A small AUV "MR-X1" was developed in 2000 for detailed investigation of the seafloor and marine organisms at JAMSTEC (Japan Agency for Marine-Earth Science and Technology). In order to assure high maneuverability under low-speed cruising and good hovering performance, the motion of the vehicle is controlled by five thrusters. When the vehicle was built, PID control was implemented, but in order to improve control performance, renovation of the vehicle operating system has been ongoing since 2007, and a model based control (LQI control) is due to be adopted when this is complete.The paper summarizes the mathematical model of the vehicle and the design method of the motion and path controller, and shows successful numerical simulated results.

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Captive model tests were carried out to capture the hydrodynamic force characteristics of a ship with the azimuthing propellers (hereafter we call the ship Podded ship) which are arranged in parallel at stern part. The measured hydrodynamic force characteristics were compared with those of usual ship model with twin propeller and twin rudder. The Podded ship has better performance with respect to ship control force in case of large azimuthing angle. However, the course stability becomes worse. Comparing push and tractor types of azimuthing propeller,tractor type is superior to performance for both ship control force and course stability. Based on the measured results, a simulation model was developed for hydrodynamic forces related to azimuthing propellers. Using the model,maneuvering simulations were carried out for the Podded ship and usual ship with twin rudder. As a result, it was shown that the Podded ship does not keep to IMO criteria of 10/10 zig-zag maneuvers, even though the usual ship is no problem. It is necessary to pay attention to ensure the course stability in the new development of Podded ships.

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Course stability and yaw response of tow and towed ships are investigated by eigen value analysis based on linearized motion equations for the ships. Then, towing cable is assumed to be a truss element. We found that there exist two slewing motion modes with long and short period. The slewing motion with long period is no relation with size of tow ship and is determined by hydrodynamic characteristics of the towed ship only and parameters of towing cable such as cable length and the towing position. In short period mode, on the contrary, the natural period and the amplitude reduction time by half become long with increasing the size of tow ship. It is useful for safe towing to enlarge the size of tow ship more than towed ship. On the other hands, course unstable zone slightly increases while the tow ship becomes smaller than towed ship. Cable length and the towing position at the towed ship almost determine the course stability. The towing position at the tow ship does not influence the course stability if the position is in aft part of the tow ship. For reducing the course instability remarkably, it is useful to take the towing position at the towed ship large. The desirable value is that 2/L2 is almost 0.8 where 2 is the towing position at the towed ship and L2 the ship length of towed ship. However, the yaw response against the steering action becomes worse.

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Recently, plate thickness in mega container ships has reached the very heavy thickness range, exceeding 70mm, not common in shipbuilding. The most important requirement for ensuring structural reliability of such ships is the prevention of brittle fracture. In the previous papers, influence of applied stress, residual stress, toughness of welded joint, weld heat input and texture of base metal on brittle crack propagation was analyzed based on a fracture mechanics model developed by the authors. And influence of these factors was almost clarified. Based on the above results, brittle crack propagation behavior at Butt Shifted Welded Joint is analyzed using the improved numerical model. For mega container ships, brittle crack propagating in the hatch side coaming must not break into the upper deck side welded joint. Numerical simulations are carried out for various conditions, and it can be said that distance between weld of the hatch side coaming and that of the upper deck must be larger than 300mm for prevention of continuing brittle crack propagation.

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The characteristics of Fatigue Damage Sensors (FDS) that are in use for fatigue life estimation of monitoring structural members in ship structures are discussed in order to improve prediction accuracy of estimated fatigue life exposed to random wave loads such as storms under various loading conditions peculiar to ship structures. Coefficients affected by loading histories against constant amplitude loading and mean stress levels are introduced for the estimation procedure using FDSs and confirmed by a series of fatigue testing and numerical simulations. This newly proposed fatigue life estimation procedure using obtained coefficients is checked by comparison results of fatigue test for large size structural model on which FDSs and strain gauges are provided simultaneously and to which random loads by assumption of storm patterns are applied under various mean stress levels.

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Applicability of slice synthesis methodology with weight function to calculate stress intensity factor and crack opening displacement in elastic condition for three dimensional cracks is investigated. Although slice synthesis methodology has already proposed, quantitative investigations of the applicability seem to be insufficient.The authors make it clear the applicable limits to the embedded elliptical cracks by comparing conventional formula based on finite element analyses. It is confirmed that the ratio of crack depth to plate thickness or back surface affects the accuracy of elastic crack opening displacement and stress intensity factor by applying slice synthesis methodology.Besides, the authors suggest modified SSM which enables to evaluate the effect of back surface. And it is concluded that modified SSM enables to give stress intensity factor and crack opening displacement of embedded cracks in elastic condition with high accuracy.

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Applicability evaluation of the developed weighth function based strip yield model for an embedded crack by applying the slice synthesis methodology ln elastic-perfect plastic bodies under monotonic uniform loading is performed.Although the weight function based strip yield model for a part-through semi-elliptical surface crack was proposed by Daniewicz and Aveline (2000), applicabl egeometries of cracked bodies is limited. Their proposed strip yield model treats only a semi-elliptical surface crack in semi-infinite bodies. Besides, quantitative investigations of the applicability seem to be insufficient.The authors proposed the improved strip yield model with slice synthesis methodology for an embedded crack, which enables to treat the finite boundary proplems. By applying proposed model, the back surface effect of the crack opening behavior and the plastic zone growth can be considered.The validity of improved strip yield model for embedded cracks is confirmed by comparing crack opening profiles under some crack geometries with elastic-plastic finite element analyses.

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This paper deals with the Design Process Simulator which can examine the influences of the differences of design processes on the performance of the designed product, quantitatively. In order to realize this, ship design is divided into two problems, i.e.design process planning and product design, and a new design support system has been developed in which product information is automatically generated by using the optimization method based on the design process information given by the designer. The characteristics of the proposed system are following points: 1) The design process is described in the system by combining the components which are the base units of the information processing to generate output data based on the input. 2) Optimization problem is automatically defined based on the design process expressed with the chain of components, and optimum product information is generated by executing the optimization. 3) During the optimization described in above 2), not only the optimum solution but the solutions in the middle of the optimization processes are also managed in the system. Robustness of the design process is evaluated by the use of these data in addition to the performance of the product. 4) In order to realize above 2) and 3), design process manager is defined. 5) Re-design and feedbacks of the design are also achieved in the system by describing the conditions of feedbacks into the design process manager.Based on the above discussions, the prototype system of the Design Process Simulator has been developed. Moreover,examples of the design process simulations intended to the ship initial design stage are shown in the paper. Thereby, the validities of the proposed method are shown.

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This paper presents an automatic design algorithm for pipe arrangement based on equipment arrangement figure and pipe diagram. Firstly, a pipe arrangement design problem is proposed for a space in which pipes and objects co-exist considering branches of the pipes and valve arrangement. This problem includes large-scale numerical optimization and combinatorial optimization problems, as well as peculiar characters of pipe arrangement design. For these reasons, it is difficult to optimize the problem using usual optimization techniques such as Random Search. Therefore, secondarily, a genetic algorithm (GA) suitable for this problem is developed. Lastly, the proposed method for optimizing a pipe arrangement efficiently is demonstrated through computational experiments, and remarks are provided for applying this methodology to a practical pipe arrangement design.

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Our current research has developed an automatic design algorithm for pipe arrangement based on equipment arrangement figure and pipe diagram. This paper firstly presents an evaluation method of valve operationality for the automatically designed pipe arrangement. Secondarily, a pipe arrangement design problem is proposed as multi-objective optimization problem, and multi-objective genetic algorithms (GAs) suitable for this problem are developed. Finally, the proposed method for optimizing a pipe arrangement efficiently is demonstrated through computational experiment, and remarks are provided for applying this methodology to a practical pipe arrangement design.

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The Japanese occupational accidents has been continued to decrease since the Industrial Safety and Health Law was established in 1972. But, in recent years, number of occupational accident at shipyard is shifting from approximately flat to increase, and also the probability of death accidents is still high as compared with them in other industries. Besides, Industrial Safety and Health Law was revised in 2005, this law recommends implementation of risk assessments for promotion of occupational safety management to the broad industrial sectors.The falling type accident is deal in this paper mainly, because this type of accident is happen 30% of occupational accidents in shipyard. This feature of falling type accident breaks out during walking on circumstances of ship construction fields, according to analysis of our constructed occupational accident database.For understanding the factors of introduction to harmful walking mode, experiment on transferring platform mock-up is attempted. And the motion of center of gravity of human body under some harmful walking environmental condition is measured by motion capture technology on video imaging analysis. The relationship with the fluctuation property of traces of center of gravity of human body and walking environment is found out, through these experiments and fluctuation analysis by method of recurrence plot on applied chaos theory. This numerical calculating methodology is proposed as evaluation of safety of walking environment on improvement of occupational health at shipyard.

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A method to retrieve knowledge of trouble in the workshops is proposed in this paper. This method can collect similar troubles from a collection of surveyor's reports composed of natural language using text-processing and ontology. This method has two steps.First, text-processing for the surveyor's reports is performed. By analyzing the result of text-processing, the information on trouble in the fabrication is normalized to a pair of component and trouble names. Second, the words which have similar meanings with the trouble information are listed by ontology. The trouble information and the listed words are then stored in a database as one record.This database is called failure information database. Classification of similar troubles can then be performed by searching the failure information database based on the surveyor's reports. The presented method is verified by using actual reports in a shipyard. The result shows that the method can obtain knowledge. For example, it was found that machine parts are often located in wrong or inappropriate positions. This kind of knowledge is useful in the design phase to avoid committing the same mistakes.

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Recently, fast car ferries of catamaran type have become larger and larger. In beam waves, motion of catamaran is relatively severe because of its large stability. Therefore, in beam waves, tilt or turn over of cars is concerned for such catamarans. If relationship between wave height and tilt of cars is clarified, safety voyage without lashing will be able to judge before sailing from port.A method of judgment of tilt of cars on deck was proposed by Kuwano. In this method, however, only rolling motion is taken into account. It is necessary to take other motions into account for higher precision of the judgment of tilt of cars on deck. A new method considering heave, sway and pitch as well as roll motion is developed in the present paper. Model experiments to check out the relevance of the new method and the effect of motions except rolling on behavior of vehicles on decks are carried out.The method is applied to a 112m wave piercing catamaran, and criteria of wave height for tilt of vehicles on decks are predicted.The predicted results demonstrate the effects of other motions except rolling are significant in some cases. It is confirmed that the most critical wave period of tilt of vehicles on decks of the wave piercing catamaran is about 6.0 to 8.0 seconds.

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