A numerical method is proposed for analyzing the potential flow around a lifting body such as a wing, a rudder, and a propeller. The method is different from the panel method in which boundary surface of the lifting body is divided into panels. In the present method the boundary surface is treated as continuous surface and the unknown (potential on the surface) is also expressed as the continuous function. So we call the method “continuous method”. In the method the boundary integral equation is solved as accurately as necessary for the purpose using automatic numerical integration routine.
Numerical results by the present method are compared with the analytical solution in case of a sphere, an ellipsoid, and a Kármán-Trefftz aerofoil. The comparison shows the accuracy of the method. Finally numerical results are shown for a circular wing and the results are compared with other methods such as the panel method and the lifting surface method, and also compared with experimental results. Those comparisons show the validity of the present method.

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The incompressible Reynolds Averaged Navier-Stokes (RANS) code using the multiblock grid method has been developed for simulating the steady free surface flows over ship having complex geometries. “Horizontal Mode”, “Vertical Mode” and “BJ-SGS” which are methods of updating boundary conditions on block interfaces are incorporated in the present code and investigated in the computation of free surface flows about Wigley hull. The new code is applied to computation of transom stern flow about a container ship and a high speed vessel and those numerical results are compared with the experimental results.

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For the purpose of simulating ocean turbulence in the artefact scale in the future, we conducted basic research on DNS (Direct Numerical Simulation) and LES (Large Eddy Simulation) of homogeneous shear turbulence in thermal stratification. Here we focused our attention on the applicability of anisotropic LES turbulence models. Firstly, the known characteristics of the homogeneous shear turbulence were reaffirmed with the DNS results. This fact may validate our numerical simulations. Secondly, the LES models were tested for the Richardson number of 0.2 and the Reynolds number of 25700. The initial Taylor-microscale Reynolds number, which denotes the intensity of initial turbulence, was set to be 22.36. We found that neither the classical Smagorinsky model nor the recently proposed Structure-Function model are able to represent the energy spectra very well at higher wave numbers and that the anisotropic LES models perform better in fitting the DNS data than the isotropic models do. Particularly, SGS (Sub-grid Scale) stresses were simulated well by the Dynamic Two-parameter Mixed model. It is thought that the concept of scale similarity and the consideration of the Leonard and cross terms can elucidate appropriate SGS energy dissipation.

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CFD simulations have been utilized to improve a hull form. As a result, a huge amount of numerical data has been acquired. In the verification process of numerical results, comparison among data obtained from different kinds of resources (e.g. experiments, other numerical experiments) plays an important role. Remarking the comparison process among data, it is found that the most difficult issue is the difference of locations that the data is defined. In this paper, we try to solve this problem. First, drawbacks of image data for the comparison in a wide spatial region are clarified. In order to overcome the drawbacks, a concept of the comparison space is introduced. Second, how to construct the comparison space is described. Finally, several numerical experiments are demonstrated to validate our concept. In the case of the linear advection problem, a new characteristic feature of the numerical error is found. In additions, it is shown that the grid dependency on the numerical results can be found out in the wide spatial region.

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It has been considered that patterns of limiting streamlines are deeply related to a formulation of longitudinal vortex around a hull. Several approaches visualize the patterns on the surface have been proposed in experiments and CFD computations. It is not easy to efficiently obtain limiting streamlines owing to several issues on the conventional visualization techniques. In additions, considering the quantitative feature of the visualized results, a certain type of visualization error will be produced in the case of the hull that its shape is long in the streamwise direction. In practical cases, it has been reported that the patterns of limiting streamlines depend on the visualization software to be utilized. In this paper, firstly, we develop a visualization technique of limiting streamlines using PEM (Pixel Exposure Method) to overcome the drawbacks of the conventional methods. Secondly, numerical errors in such visualization are pointed out, and propose a way to reduce the visualization errors. We will visualize several results obtained from the Direct Numerical Simulation (DNS) by proposed method. It will be shown that our procedure of the visualization which the whole region of the surface is visualized by PEM and the detail is explored by a highly accurate particle tracking is suitable for inquiring a structure of the flow fields.

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The mechanism of cloud cavitation generation from a sheet cavity on a foil section has been studied by several researchers. It has been revealed that re-entrant jet cuts the leading edge of sheet cavity and breaks the clear vapour structure into small bubble clusters as cloud cavity. However, the detailed picture of the sheet cavity cut-off phenomenon is still missing. In this study, we carried out experimental observations of sheet-cloud cavity on a NACA0015 foil section using high speed video and hot wires mounted on a foil surface in order to clarify quantitative characteristics of re-entrant jet and its role in sheet cavity cut-off phenomenon.The results of experiments have shown that there were several patterns in the sheet cavity cut-off phenomenon, and that the thickness of re-entrant jet is an important factor.
We have also carried out numerical simulations for the same test case. The numerical simulation was performed using a commercial CFD code STAR-CD and the Bubble Two Phase Flow cavitation model implemented in the code. The simulation reproduced unsteady shedding of cloud cavity, although some differences were found in the detailed features of the flow.

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Comprehensive experimental studies regarding ship motions and wave loads using two different types of merchant ship models : a VLCC model and a large-container ship model, have been conducted respectively in order to investigate the nonlinear characteristics with respect to waveheight of motions and wave loads in large waves.
Six degrees of motions, vertical as well as horizontal bending moment and hydrodynamic pressures were measured in a quite systematic manner in different wave encountering angles, different wave frequencies and different incident-wave heights as the ship models were freely advancing without any external restrictions.
The nonlinear characteristics of the two different types of merchant ships observed in ship motions and wave loads are discussed in detail with obtained experimental results and numerical ones calculated by means of strip method. As the results of these studies, the followings may be concluded.
1) Nonlinearities with respect to waveheight are confirmed in such a way that the motion responses per unit incident-wave amplitude become smaller as the waveheight increases, which are especially remarkable in rolling and heaving motions.
2) The nonlinear waveheight characteristics of the hydrodynamic pressures are observed distinctively not only at the locations near the water-surface but also at the locations well bellow the water-surface.
3) The nonlinearities of the wave loads on the VLCC model are relatively small but were manifested in the container ship model especially in quartering seas.
4) It is characteristic that nonlinear characteristics are persistently observed in virtually any responses of the container ship model advancing in quartering head seas, which may be caused by the geometrical features of the container ship such as the large bow-flare.

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Wave basin experiments of a blunt ship model were conducted comprehensively in regular and irregular extreme waves. Six degrees of motions, vertical as well as horizontal bending moments at the midship section, hydrodynamic pressures on the hull at 20 locations, relative wave elevations at 5 locations and green sea loads on fore deck and two hatch covers were measured in a quite systemic manner. The selected regular wave conditions were 5 different wave encountering angles, 6 different wave frequencies and 4 different incident-wave heights, while the selected irregular ones were only the head and beam seas with the significant wave height of 10.6 meters and the mean wave period of 14 seconds. The main purpose of the experiments is to investigate and understand the characteristics on the wave-induced motions, hydrodynamic pressures and loads in extreme waves especially as the green sea loading on the decks. And the final objective of this study is to establish practical approaches of evaluating wave loads in extreme waves qualitatively and quantitatively. As the first report of this study, this paper mainly introduces the results obtained by the experiments. The nonlinear characteristics with respect to wave height of wave-induced ship motions and loads in extreme waves are also discussed with the phenomenon of the green sea loading on the decks.

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A series of model tests in waves were conducted to measure the green sea loads that act on deck and hatch covers due to shipping water. A model of bulk carrier was used. The tests were carried out in irregular waves of which significant height is 10.6 meters and peak period is 14 seconds. In order to discuss the effects of wave heading and ship forward speed on the green sea loads, the model tests were made in several combinations of wave heading and ship speed conditions. It was confirmed that the deck wetness and green sea loads will be reduced considerably if the wave heading is altered to the quarter or beam seas or the ship speed is reduced.
In order to assess the experimental results quantitatively, green sea loads were estimated by the practical estimation methods that were developed by the one of authors. Having compared with measured results, it was found that the estimated results were in good agreement with measured ones. It is concluded that the experimental results were rational.
Comparison of green sea loads between measured results and present rules, ICLL66 and IACS UR-S21, was made. Although it is difficult to directly correlate measured values with the rules, mean values tend to be larger than the ones of ICLL66. It is also found that the green sea loads defined in IACS UR-S21 is ranked to somewhere between 1/10 and 1/3 significant values in relation to the measured results.

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Wave-induced ship motions, loads and hydrodynamic pressures are evaluated by a Rankine source method for two different types of practical merchant ships : a VLCC and a large-container ship. The numerical results are compared with the experimental results obtained by the authors. They are also compared with the results calculated by means of a modified strip method in order to investigate the three-dimensional effects on ship motions, bending moments and hydrodynamic pressures. The relationships between hull characteristics of the ships and their hydrodynamic responses are discussed in detail. It is concluded that the Rankine source method could be an effective numerical tool for the evaluation of wave-induced loads acting on practical merchant ships and thus may be used in the structural design of practical ships.

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Typical factors of ship structural failures are corrosion and fatigue clack of the members. Although these failures can be detected during an inspection and examination and repaired, it is very difficult to estimate when and where these failures break out in the ship structure. Evaluation of ship structural safety can be conducted by the assessment of the capability of the structure to take into account the effect of corrosion of members and the demand based on the encountered wave conditions.
In this report authors study a structural safety assessment procedure of an aged ship based on structural monitoring data. This is the first report concerning the evaluation of wave-induced load of a 1000 ton class patrol ship equipped with structural monitoring system. The encountered wave conditions and sailing conditions are examined by the structural monitoring responses and log book records. Authors developed the estimation method for the relative angle between wave direction and ship heading course and the mean wave period of irregular waves from the correlation coefficient between pitching rate and midship deck stress measured by structural monitoring system. Based on the estimated sailing conditions and analyzed wave condition of long-term statistics of observed wave data recorded in the log books, the long-term wave-induced responses of the ship are estimated and compared with measured data.

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In GPS kinematics measurements, the baseline length has significant effect especially on the determination of the initial phase ambiguities. In VD (Variance Detection) method, the ambiguities are not required. In the present paper, the Effects of baseline length in VD method is discussed. The effects seem to be small
RTK (Real Time Kinematics) and VD (Variation Detection) methods are combined, and measurements in very wide frequency range from the direct component to very high frequency component become possible. RTK and VD are used at long and short epoch, and they measure low and high frequency components respectively. The results by RTK and VD are then synthesized. This method has been applied to analyze motions of a buoy installing a GPS antenna and floating on sea surface. The results obtained in this way seem to give quite reasonable ones.

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This paper describes a measuring device using piezoelectric material, which was developed to monitor features of the stress history of a structural member. The device counts the number of cycles of the fluctuating stress by the level crossing count method and the rain flow method. Microcomputers are used in this device to perform operations of those counting methods. The device can also display the operation results and the stress level of the monitored structural member with the liquid crystal display (LCD).
In order to see the performance of the test manufacture of the measuring device, experiments were carried out using a fatigue testing machine. The strain detector using piezoelectric polymer film was bonded onto a smooth specimen and multiple repeated stresses were applied to that specimen. As the result, the stress history measuring device can operate under a stress range from -110 MPa to 110 MPa, and a frequency over 1 Hz. Then, the device using the level crossing count method and the rain flow method can count accurately the number of cycles of the fluctuating stress.

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In this paper, wave drifting speed of a floating body is discussed.Measurements of wave drifting speed were conducted on both two-dimensional floating body and three-dimensional floating body. Then, the theoretical calculation method of wave drifting speed was derived from the analyses of measurement results.
The mechanism of wave drifting speed varies with wavelength. In the range of short wavelength, wave drift force due to reflection waves drifts the floating body; therefore the drifting speed is decided by the equilibrium of wave drift force and fluid drag, and it is proportional to the wave sloop. In the range of long wavelength, on the other hand, wave drift force hardly acts on the floating body, because wave almost transmits the floating body; therefore the drifting speed is decided by the wave-current speed and it is proportional to the square of the wave sloop. Taking these wave drifting mechanisms into consideration, an estimation method of wave drifting speed, which covers entire wave range, is proposed.

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Because of the ship maneuvers, such as changes of the course and the speed, ship motions in waves are regarded as a nonstationary random process, even on the assumption that the seaway can be considered as stationary stochastic process. In order to cope effectively with the nonstationarity, T-VVAR (Time Varying Coefficient Vector Auto Regressive) modeling with the instantaneous response is introduced. The procedure has the significant merit that it can be estimated by independently fitting the univariate models for each component. In order to fit the model to the data recursively, T-VVAR model is transformed into the state space model and the time varying coefficients can be evaluated by using the Kalman Filter algorithm. Using the estimated time varying coefficients, the instantaneous ship motion cross spectra can be calculated every moment.
In order to examine the reliability of the proposed procedure, onboard tests were carried out.Under the stationary conditions, on the constant speed and course, the proposed method shows good agreement with the SVAR (Stationary Vector Auto Regressive) modeling analysis. Moreover, it is shown that the proposed method can estimate instantaneous ship motion cross spectra even if the speed or the course is changed. This concludes that the proposed method is a powerful tool for on-line analysis of nonstationary ship motion data. The results of these tests are shown and problems encountered on applying are reported.

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The component-type mathematical model of ship hydrodynamic forces developed by us can describe precisely the oblique hydrodynamic forces over the range of drift angle |β| = 0 90° or 90 180°. It also can estimate satisfactorily the turning hydrodynamic forces X, Y and N in the simulation of steering motion through the oblique hydrodynamic forces. The mathematical model shows the quantitative discrepancies in the estimated Y hydrodynamic forces of pure (β = 0°) and lateral (|β| = 90°) turning motion. This paper offers a solution to these discrepancies by adding the horse-shoe vortex system and the additional effect of the cross-flow vertical vortex system, which are located at midship part and caused by turning motion, to the conventional vortex systems presented in the previous paper. The characteristics of the oblique hydrodynamic forces can estimate precisely the linear derivatives Y_r and the large effects of cross-flow drag in turning motion.

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Twin screw ferry with bow thruster can crab actually to leave/approach the bank by suitable operation of 2 propellers, 2 rudders and bow thruster without assistance of tugs. Then, it is known that the effect of propeller rotational direction such as inward/outward on the crabbing performance is considerably large. To grasp the flow mechanism with respect to the effect of the propeller rotational direction on the crabbing, we carried out free-running and captive model tests using a ship model with 7.10m in the length. The bow thruster model, propeller and rudder models are installed to the ship model together with the equipment for measurements of the horizontal motions and the hydrodynamic forces. As a result, we found that outward-FPP/inward-CPP in the usual operation is the best combination and additional lateral force acting on the hull induced by slip stream flow from a propeller with reverse direction exerts considerable influence on the crabbing performance. The model test results were confirmed by the calculation using a 2D hydrodynamic model.

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A finite-volume method is developed for the motion simulation of a sailing boat in oblique waves. The solution procedure for the Navier-Stokes equation is connected with that for the motion equations in three degrees of freedom, that it, pitch, heave and roll motions. The O-H type boundary-fitted coordinate system is employed and the motion of the boat is represented by external forces in the Navier-Stokes equation. A unique technique is to rotate the free-surface in accordance with the pitch and roll motions of the boat. The availability of the present method is demonstrated by the simulation of America's Cup class sailing boat with and without keel and sail.

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The Marino Forum 21 started an R&D project in fiscal 2000 with grants from the Japanese Ministry of Agriculture, Forestry, and Fishery to develop the equipment for the eutrophication of the sea by upwelling deep ocean water, sending into euphotic zone and increasing phytoplankton.
First, some concepts of moored floating structure with a riser pipe for deep ocean water upwelling at the water depth of 500m were investigated and evaluated by computer runs. Second, based on the investigation, basic design of the structure was undertaken. Next, scaled model tests were carried out in an experimental tank at several wave conditions in order to evaluate dynamic response of motion of the structure, mooring force and riser pipe stress. Finally, based on this experiment, possibility of the structure and validity of the computation were verified.

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In our first report, we presented a methodology for determining the critical metacentric height of an Indonesian RoRo passenger ship in the light of the annual capsizing probability calculated with the piece-wise linear mathematical model and existing wave statistics. Then, the second report, with this methodology and more realistic data sets, concluded that the calculated annual capsizing probability of the Indonesian RoRo passenger ship almost coincides with the actual casualty statistics. In the present report, the authors attempt to take some human elements, e.g. judgement of the ship masters to avoid bad weather and effects of overloading, into account for estimating the capsizing probability based on the above method. By comparing it with acual casualty statistics, the frequent capsize of Indonesian RoRo passenger ships can be reasonably well explained with these human elements.

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An offshore trawler “Ryuho Maru No.5” capsized and foundered off the Erimo Cape of Hokkaido on 11 September 2000 in moderate sea condition. In this paper the factors related to the accident are evaluated.
As the main factors followings are listed;
1. hauling much amount of fish on the upper deck,
2. rough manoeuvring,
3. movement of unlashed items on board, and
4. movement of the cod end with fish over the inner bulwark.
Evaluating the effect of each factor on stability and on heeling moment, the sequence and mechanism of capsizing were clarified from the energy balance like the C-coefficient concept.
Moreover the effects of dominant factors are investigated through a parametric study. It is clarified that the heavy cod end on deck and centrifugal force by hard turning are of prime importance because the former not only reduces the stability but leads to heeling moment, and the latter keeps working along the capsizing motion.

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There is some problem that characteristics of databases differ mutually though there are several current available long-term wave databases. In the previous work, it was clarified that the databases of long-term waves by visual observation have a consistent distortion tendency, and some restoration techniques of them were suggested. In this work, adding some supplements to the previous work, the properties of a long-term prediction of added wave resistance and the midship vertical wave bending moment by using the restored wave databases are investigated.

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It is well known that a ship can be regarded as a type of wave recorder and, under the assumption of linear superposition, wave spectra can thus be estimated from measured ship motions. Based on this idea, the evaluation of directional wave spectra has been extensively carried out in recent years. However, when a ship is traveling with an advance speed in following seas, there is a range of the encounter frequency of the ship, which cannot be related to the wave frequency by a single-value transformation. In the previous paper, we proposed a method to overcome this difficulty, and evaluated one-dimensional wave spectrum by using nonlinear programming.
In this paper, we extend the method used for the estimation of one-dimensional wave spectrum to evaluate the directional wave spectrum. The capability of this approach has been discussed by comparing the estimated average wave periods and significant wave heights with those evaluated from the so-called SMB Method and the observation data written in logbook.

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According to the first report, not only the position of a sea bottom transponder but also the underwater acoustic velocity can be determined, if the position of sea surface transponders and the distances between the surface and bottom transponders are known. In the second report, a theoretical possibility of obtaining the position of the sea bottom transponder with accuracy of centimeter order is shown. For the purpose, estimation of the underwater acoustic velocity distribution as a part of solution is extremely important. Effects of errors in the positions of the surface transponders and the distances between the surface and bottom transponders are also obtained in detail. In the previous papers, two dimensional calculations are conducted.
In the present paper, more realistic simulations are conducted by introducing three dimensional calculations. And a new idea called MIL (Method of Incremental Layers) are developed to stabilize numerical calculations.

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For the ocean development, work vessels are important. The operability of such vessels are heavily affected by sea conditions. Here, for increasing the operability of floating cranes, we tried to suppress the swinging motion of a load in waves.
For that purpose, we developed a control system of the swing of a load, through controlling body motions of a floating crane, and also developed a numerical simulation method for this estimation. Furthermore, we adopted the so called pneumatic control system for controlling the motion of a floating crane.

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This paper is the third report that describes the application of the Least Square Method to analyze the Kochin function of the radiation waves and diffraction waves obtained by the Projected Light Distribution Method. The previous papers used only one line transverse cut data instead of two-dimensional data provided by Projected Light Distribution Method. The results are compared with the longitudinal cut method proposed by Ohkusu and with the previous result as reported in the first and second reports. The detail description about the effects of the integration region is also described.

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Recently, new type of equipments using density current are applied to improve water quality in enclosed bays such as Gokasho Bay and Ohmura Bay. In order to obtain a knowledge on diffusion by density current in the topography of real sea, hydraulic model experiments were carried out by using the distorted models installed in the rotating tank which could simulate the effect of the earth's rotation. In the experiments, density current was produced which is intruded between the stratified two water layers with different density, for the purpose of examine the effects of the equipments of improving water quality. A new similarity law was proposed to reproduce density current under the distorted model. In the analysis procedure, a technique was established which measured the distribution of dyestuffs concentration by means of the luminance method. Then, effects of tide, density current, the earth's rotation on the material diffusion under the topography of real sea was examined.

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Recently monitoring of sea healthiness using voluntary observation ships has been carried out. In the monitoring, seawater is sampled through an inlet located on a ship hull, and the sea healthiness is evaluated through analyzing sampled water chemically and biologically. In the coarse of analyses, the information of original position of sampled water is one of important factors to assess the sea healthiness, however its quantitative evaluation has not been carried out.
The objective of the research is to develop the method to estimate the original depth of sampled water. In order to do that, first of all, we use a model ship experiment. In the experiment, we inject dye from the upstream of the ship and pick the water up from the inlet, and then dye concentration in the sampled water is analyzed using a spectrophotometer. The concentration is mapped onto the position of dye injection and we thus show the original location of sampled water as a contour map on the upstream sectional plane.
Further, numerical simulation of flow around ship is done and by solving a diffusion equation, upstream location of sampled water can be evaluated numerically and we show that numerical evaluation agrees with the results of experiments.

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We began to develop the oil sorbent made of organic waste material in order to provide the resources for marine oil spill response with less environmental load and cost. After some screening, it was found that the fiber of Sugi (Cryptomeria japonica D.Don) bark has potential to be excellent oil sorbent because of its hydrophobic and oleophilic character. As bark fiber can be used with enclosing cotton sheet, the products consist of completely organic materials. When the bark fibers of SBS were in drier condition and their size were larger, SBS performed better absorbency. SBS performed equivalent absorbency (picking up at most 13.4 times their own weight in bunker A) as conventional polypropylene sorbent in laboratory experiment. In water tank experiments, we also confirmed that some shape of SBSs such as S25, S50, B6S14 and M50 could successfully work for recovering oil in small wave and current, which would be expected as production models.

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In stormy weather on January 2, 1997, the Russian tanker “NAKHODKA” broke up at midship into two parts in the Sea of Japan just, off the Japanese coast. The recovery operation was hampered by high waves, and the most serious problem was the lack of equipment to recover the spilled oil operable in stormy weather. In 1998, corresponding to this accident, the Association for Structural Improvement of the Shipbuilding Industry (ASIS) initiated a three-year research and development project on large-scale recovery systems to collect highly viscous oil with a minimum kinematic viscosity of 0.1m²/s for severe sea conditions.
This paper focuses on the selection of an oil skimmer system suitable for recovery of highly viscous spilled oil emulsified under rough sea-state. The oil skimmer system is composed of a float, pump, hose, oil/water separator, etc. Dynamic simulations and tank tests were performed by using several types of floats for comparative evaluation. The basic design of the oil skimming and treatment system including various devices has been completed, based on constituent technologies, which are wave-response technology, highly viscous oil suction technology (reported on first report) and highly viscous oil collection technology.

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Reduction of CO₂ emission into the atmosphere has been one of the important concerns in the various fields of human activities for prevention of the climate change in global size. CO₂ contained in the exhaust gas from ships is also considered to be the reduced one, for which improvement of ship's propulsive performance and fuel oil consumption reduction etc. has been earnestly investigated.
In this paper dissolution of CO₂ in the exhaust gas bubbles injected into the flow around ship hull is proposed to be one of the powerful candidate for resolution, taking into account the hydrodynamic characteristics of flow around ship hull and chemical property of CO₂ in the large amount of salt water around ships. The system outlined is composed of exhaust gas bubbles injection system, including power needed for injection, hydrodynamics of micro gas bubbles flowing along the ship hull of full scale accompanied with chemical process of CO₂ dissolution, reduction of ship's frictional resistance.

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The Bisan Strait Sea in The Seto Inland Sea becomes one of the main spawning grounds of the sand eel. The sand eel catch lowers over 80% in spite of the decrease of the direct sand bank area by seabed sand picking in this sea area being about 13% in comparison with 1977 ages in 1998. Then, it was made that the effect of the change of water depth by the seabed sand picking on the transportation to growth field of Japanese sand eel larvae was evaluated according to the numerical model to be a purpose for the Japanese sand eel larvae in the time in which self swimming force in the Bisan Strait sea is scarce. As the result, it was indicated that Japanese sand eel larvae transported to the growth field in the Bisan Strait west sea decreased about 17% according to the numerical model.

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This paper addresses the issue of ship routing design for collecting and transporting the oily liquid waste from a number of ports to a waste treatment center. The aim is simultaneously to construct a set of ship routes and to determine the number and the types of ships in a fleet at the minimum total cost. The problem is considered as a vehicle routing problem with heterogeneous fleet of vehicles and multiple trips (VRPHMT). The VRPHMT is a combination of two variants of the classical vehicle routing problem (VRP) by including two additional features. The first is the heterogeneous fleet of vehicles where number and types of vehicles have to be determined, and the second is multiple trips where vehicles may perform more than one route or trip as long as the total duration of each vehicles does not exceed the planning period.

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Structural reliability analysis of a pontoon -type very large floating structure surrounded by a gravity-type breakwater is performed for the extreme wave condition considering the failure of breakwater as well as that of the floating structure. Bending and shear collapses of the cross s ection are considered as possible failure modes for the floating structure, while an overturning failure for the breakwater.
The probability of overturning of the breakwater and the probability distributions of the transmitted wave height with and without failure of the breakwater are evaluated based on the statistics of the extreme wave height in Tokyo Bay. The ultimate bending and shear strengths of the floating structure are calculated using the Idealized Structural Unit Method (ISUM) and FEM. Based on these results, the probability of failure of the floating structure considering the overturning of the breakwater is calculated and compared with the target safety level.
It has been shown that the considered floating structure is most likely to fail in th e bending collapse mode in transverse waves and the corresponding safety level satisfies the target level.

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Slowly-varying wave drifting force has a crucially important influence on the behavior of the moored medium- sized offshore structures. As to very large floating structures, abbreviated to VLFS, slowly-varying wave drifting force plays a less important role because slowly-varying wave drifting forces on each part of VLFS have different phases and cancel one another.
The present paper proposes the phase-difference effect coefficient, which considers cancellation effect of slowly-varying wave drifting force on VLFS. The proposed method is validated with the comparison to field measurement for a 1, 000m-long VLFS. It is also shown that an assumption of perfect reflection of incident waves at VLFS' edges is valid and advantageous in designing the mooring system of VLFS.

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The marine environment around the VLFS model was investigated in the field experiment of Maga-Float Phase- II project. Continuous monitoring of vertical profile of water temperature, salinity, dissolved oxygen, chlorophyll-a and so on were carried out at several fixed stations below and around the floating structure. Additionally, manual sampling of sea water was sometimes carried out in order to investigate spatial distribution of water quality in detail. As a result, precious filed data were obtained not only for influences of VLFS on the surrounding marine environment, but also for grasp actual dynamic processes of the coastal phenomena. It can be said that the physical factors measured in the present study are affected little by the sea covering effect of VLFS. However, some local influences were found in chemical or biological factors such as nutrients and chlorophyll-a. It was found that the primary impacts of VLFS on the marine environment are caused by sessile animals on the structure. In order to clarify the extent of marine environmental impact of VLFS, further analysis is necessary using effective numerical models. The field data obtained in this study will be greatly useful to develop such models and verify them.

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Simulation study by means of coastal ecosystem model is conducted to examine the various effects of Phase-II Mega-Float model on marine environment in Tokyo Bay. As several results of field measurement around Phase-II Mega-Float model, some local impacts on marine chemical-biological environment were found; the amounts of chlorophyll-a and dissolved oxygen decrease, and the nutrient concentration increases under the floating structure. These phenomena are thought to be caused by the sessile organisms adhering to the floating structure, and are reproduced adequately by improving formulation of the biological processes related to the sessile organisms. Finally, the impacts of Phase- II Mega-Float model on the surrounding marine environment are discussed.

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Semisub-Megafloats have been studied for an offshore infrastructure. It is clear through the previous studies that wind lift force acting on the deck of a Semisub-Megafloat is very important in high winds and waves such as typhoon conditions. In the present paper, the response characteristics of Semisub-Megafloats in winds and waves were investigated. The effects of wind lift force on the response of the structure was clarified and it was shown that column supported type VLFS is desirable from the point of view of wind lift force.

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The purposes of present study are to develop the powerful numerical method for sea shock phenomenon and to clarify the characteristics of sea shock responses on very large floating structure.
The present numerical method has been considered the characteristics of propagation earthquake waves in water and seabed. Numerical computations have been carried out very large floating structures in the cases of several seabed conditions.
From the comparisons of computational results, it is that the numerical results by present method are greatly different of the results with the rigid seabed condition.

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A very large floating structure has hydroelastic responses that are an elastic deformation and a slowly varying drift motion. Usually, wave drifting forces increase when an elastic deformation is reduced by a motion reduction system.
In this study, characteristics of the hydroelastic responses of the backbone type elastic floating models with air chambers are investigated experimentally. The model tests were carried out in irregular waves using the five models. The responses include the elastic deformation and wave drifting forces. The air chambers can absorb the wave energy.
It is confirmed that the reduction system is effective for the motion reduction from the experimental results of the vertical displacements and the bending moments. Then, we know that there is no direct causal relation of the motion reduction and the wave energy absorption. And more, it is difficult to estimate the reduction effect of the slowly varying wave drifting force from the reduction characteristic of the steady wave drifting force directly.

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“Mighty Whale” is an offshore floating type wave power device based on the oscillating water column (OWC) principle. It converts wave energy into electric energy, and produces a relatively calm sea area behind it. These electric energy and calm sea area will be able to utilize for varied applications such as to improve a deteriorated ocean environment and fish farming. JAMSTEC constructed the prototype of Mighty Whale for open sea tests by May 1998, and the open sea tests were started on September 1998 at the mouth of Gokasho Bay in Mie prefecture. This paper describes the characteristics of wave energy absorption of the prototype by the open sea tests data. Particularly the results of the prediction method of electrical output and water tank experiments were compared with open sea tests data on the output of air chamber, turbine output and generated output. The outline of the discussion about these results, the validity of prediction method of generated output was confirmed. And we recognized characteristics of wave energy absorption and wave energy efficiency of floating type wave power device. Based these results, the validity of the design for the prototype was confirmed.

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“Mighty Whale” is an offshore floating type wave power device based on the oscillating water column (OWC) principle. The prototype of Mighty Whale was installed at the test location, the mouth of Gokasho bay in Mie Prefecture, on July 1998. The open sea tests were started on Sep. 1998, and we are keeping on measuring many data to show the safety and economic features of the device.
Generally, it is important to decide environmental design conditions, wind speed, wave height and so on, when we design offshore structures. Therefore, these design methods are showed by many papers and rules. However, there are few cases to verify whether design methods for actual installed offshore structures are right.
In this paper, we verify design methods by using measurement data on Mighty Whale, and have some concluded points as follows. 1) It is necessary to consider long return year (over 50 years) even if actual year is short (4 or 5 years). 2) In case of using adjacent site conditions data, it is important to consider geographical features. 3) It is practical to cut off extreme data if we decide return years by short-term data. 4) It is better to consider swell conditions by typhoon on the coasts of the Pacific.

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In the previous report by the authors, the accidents in the Japanese shipbuilding industry were reviewed and it was concluded that the accidents of falling and tumbling from the higher place had occurred frequently, and then the causes and countermeasures for them were discussed using the virtual human model.
In this paper, the same biomechanical analysis has been carried out against climbing up a ladder, passing an access opening, and walking on a scaffolding, because these are thought to have problems in the safety, and then the most suitable conditions in view of body burden have been studied using the response surface methodology; optimum climbing condition on the inclined ladder, the preferable position and size of the access opening, and the suitable walking posture on the scaffolding.

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The authors have carried out the human task simulation by a computer about the shipbuilding works in order to increase the productivity and safety so far, corresponding to the recent situation of the Japanese shipbuilding industry; decreasing of skilled workers and increasing of old workers.
This report has picked up the welding works for hull construction as a main job in shipbuilding. For the typical postures such as flat, vertical, and overhead position, the human task simulation and the metabolic energy expenditure analysis have been carried out using general purpose program “Jack”. Moreover, necessary rest time to recover the fatigue has been studied, and the optimal work cycle is examined.
As the result, it can be concluded that the flat position to weld, widely applied posture, is most severe in view of energy expenditure while the overhead position is most easy, and that the rule of “short breaks and often” is preferable from the viewpoint of recovery of the fatigue, especially for the works such that the consumption energy is large.

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In this research, the application to the work measurement in shipbuilding was examined as a concrete application example of a wearable system. Authors made the work content input system that the worker input by using the voice recognition, the speech synthesis and the positional measurement system of the worker that used a magnetic frequency. They were processed with the computer that the worker wore. The work analysis of the current state could be done at once for the acquired data, and effectiveness was found as a prototype system of the work measurement in shipbuilding.

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Authors have been developing information system to support ship inspection. In the previous reports, ship inspection is classified into three stages (Plan, Do and Check), and information system for generating inspection information and damage information was developed. In this paper, integrated information system to examine the safety of ships is discussed.
In order to realize this, some new models and functions are proposed. Most important model is “Unconfirmed damage model”. This model is defined to express damages which are not found by the inspection. The characteristic of this model is to express damage without using specific information such as position or geometry. In addition, function to forecast the growth of damages and function to assume the unfinding damages are defined to generate “Unconfirmed damage model”.
Based on these considerations, prototype system was developed. In the system, appropriate inspection can be examined with considering uncertainness of the inspection, growth of damages and the importance of structures. Some examples are shown at the end of this paper.

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For production activities very large information on process planning and scheduling is necessary. There are various restrictions in the factory. Most efficient production schedule must be planned in consideration of those restrictions. However information handled by production scheduling is huge and it is very difficult to plan the optimal schedule. Therefore, skill is needed for production scheduling.
The authors have been studying on a factory simulator that bases on petri nets and published two papers already. This paper is the 3rd report of the authors' research and presents the enhanced concept of the previous simulator. In the authors' previous papers, the working resources and operations are modeled as petri nets, and the shipyard simulator is implemented by using of petri nets. In this research, authors propose the petri nets that are including the restriction of working resources in shipyard.
We aimed to implement the factory simulation system of the shipbuilding more realistic than ever. We have already implemented the production scheduling support system in the shipyard that is part of our research in CIM for shipbuilding. In order to use this result of our research more, we implement the system that can evaluate the effectiveness of generated production schedule by the factory simulator. Time is freely controlled in the computer and we implement the shipyard simulation system that can simulate the process of the production activity in a shipyard.

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In modern shipyards, the block construction method is widely used in building ship hulls. But with this method, when work falls behind schedule the results include downtime, cost increases, and delivery delays. Therefore, an efficient schedule is strongly required. However, a large number of blocks with different sizes and shapes and different procedures must be considered. In addition, the existence of several objectives, such as total cost reduction, shorter completion period, efficient workforce allocation, make the problem more difficult. The block construction schedule is, in short, so complex that veteran engineers usually resort to a rule of thumb in preparing it. For these reasons, an obtained schedule is not necessarily an efficient one. To improve this situation, we must optimize schedules rationally and obtain practical solutions that satisfy all of these requirements simultaneously. Thus, the Multi-Objective Genetic Algorithm (MOGA) is utilized in this study. MOGA applies a Genetic Algorithm (GA) using the concept of Pareto optimization for multi-objective optimization. This method uses the GA characteristics of collective evolution of a solution group. This makes it possible to efficiently arrive at a practical solution from an almost infinite number of solution candidates. This study produced useful information, such as the trade-off relation between overtime work and a shortened completion period, the Pareto solution for total workforce and total completion period, and optimum worker assignment.

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Various systems that support the production planning by such as an automatic generation systems of the assembly procedure and the best scheduling are developed. However, it is difficult to say to support the entire production planning integrated. So, the integration of a variety of information processing in the planning is expected. Information on the production plan is not generated at a certain stage alone at a time, and planner has to generate information phased and growing up by changing his view of a plan from global aspect to local aspect.
In this research, the authors paid attention to a phased information processing of the production planning, and consider the management of job information to integrate the each planning level. The network model of information is applied as an integrated model to manage a phased generating and processing of job information. The composition (has-a) relation between an upper layer job and relation and a lower layer ones is proposed in this model and integrated management of various hierarchies of the production planning is proposed by describing the job model and the relational model of job positively.

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The transient 3-dimensional temperature distribution within the gas flame during line heating is measured in detail by a high performance L. I. F. measurement system. It has been found that the relative distribution of gas temperature around the torch is almost the same as that in spot heating. It has also been found that this relative distribution is almost unchanged regardless of the temperature increase in the steel plate. Thease results lead us to a new hypothesis that the relative distributions of gas temperature and local heat transfer coefficient around the torch remain unchanged and they are almost the same as those in spot heating during line heating process. A new method of heat input estimation for line heating process based on this hypothesis has been propounded.

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