In order to discuss water wave problems in unlimited waters, it becomes very important what kind of wave radiation should be placed on a virtual surface corresponding to infinity. For this kind of problem, Sommerfeld radiation condition is well known. In the present paper, the condition is extended to treat a case with an incident wave. Furthermore, a more general wave radiation condition are introduced from a different point of view.
The above mentioned wave radiation conditions are included into the variational principles of Kelvin, Hellinnger-Reissner and Dirichlet type. Then, the Dirichlet type variational principles are used in numerical calculations for bending waves of a bar, and the effectiveness of the wave radiation conditions and the variational principles are shown.

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A free-surface boundary element method is presented for solving three-dimensional steady ship wave problem. The method approximates geometry and potential with a higher degree of continuity, compared to the other Rankine source methods. Global parametric B-spline tensor products define both the ship hull and the free-surface geometry. A skinning type algorithm based on de Boor procedure is developed to perform the surface fitting. B-splines of various degrees represent the unknown singularity distribution. The functions describing geometry and potential have independent structures and are connected on their parametric space. The influence coefficients are evaluated by adaptive Gauss quadratures after removing the singularity of Rankine source analytically. Kelvin's type free-surface condition and Kutta-like radiation condition ensure unique solutions. Involved derivatives of the potential are obtained directly, without using a difference scheme. Computations of the wave resistance for Wigley, Series 60, HTC container ship and SR221B tanker hull forms, approximated by a single patch, demonstrate the accuracy of the method.

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When a ship with a wide transom stern runs on a deeper draft than design draft, forward-oriented wave breaking with high turbulence intensity often occurs just behind the transom stern. To prevent or decrease the phenomenon is important for energy saving for such ships, because it generates large hull resistance.
The phenomenon is affected by viscous boundary layer formed on the stern bottom just in front of it. Its characteristics are, therefore, more complicated compared with those of similar phenomena observed around bow or in hydraulic waves at shallow water.
Based on such understanding of the phenomenon, studies are made to get knowledge effective for transom stern design, i. e., on how to treat the phenomenon, main design parameters ruling the phenomenon and characteristics of the resistance due to the phenomenon.

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Impellers of controllable pitch side thrusters are operated under the condition of the pitch angle twisted largely from the design geometory (0° (zero) pitch angle). Therefore, it is very important to consider changes of the geometrical shapes with the twist of impeller blades and their performance characteristics in the design of controllable pitch side thrusters.
In the present paper, two impellers of the forward skew type (A) and the backward skew type (B) are designed and the above-mentioned changes of the geometrical shapes with the twist of impeller blades are calculated and their open water characteristics are investigated theoretically and experimentally. The open water characteristics of these two impellers were calculated by using the propeller lifting surface theory. Then, open water tests were performed by using the impeller models with and without the duct in the towing tank.
These results show that the camber of the blade section becomes minus largely with the twist of impeller blades and the open water characteristics with and without the duct deteriorate in case of the backward skew type (B) comparing with the forward skew type (A).

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In the usual linear wave-body interaction problems, the variation of the space-wise mean level of the free-surface is ignored and the free-surface boundary condition is imposed on the calm water-surface level. In some problems, however, the variation of the mean free-surface displacement can be so large that it can no longer be ignored even in a linear theory. In the present paper, the formulation that accounts for such effect is presented. As an example application of the presented formulation, the water-surface displacements associated with an oil recovery ship, part of which consists of a water-way bounded by a shallow bottom plate, are computed and compared with experimental results.

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Munif et al. had proposed a 6 degree-of-freedom (DOF) nonlinear mathematical model for predicting extreme roll behaviors and capsizing for a ship in astern waves with a moderate forward velocity. To validate this model, the authors carried out several numerical runs at the condition corresponding to the free-running model experiment by Hamamoto et al. The comparison in time series and capsizing boundaries between the model experiment and the numerical simulation shows a reasonably good agreement. Furthermore, by comparing with the 4 DOF mathematical model excluding heave and pitch motions, it is revealed that the effect of heave and pitch motions can be significant when the wave steepness becomes larger.

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A model test in regular waves was carried out in order to develop a method for estimating horizontal impact pressure which acts on the structures on deck due to shipping water. A model of a cargo ship for Japanese domestic voyage was used. The bow flare form and bow height were varied from the original one to investigate the effect of them on the horizontal impact pressure. It was found that the effect of bow flare form is small compared to the one of bow height.
The theory of “flood waves” was applied for evaluating the shipping water height distribution on deck. The inputs of this method are relative water height at bow and pitching angle those can be calculated by strip theory and so forth. Having compared with measured data, it was confirmed that this theory can give a good estimation for the shipping water height distribution.
The Wagner's theory of wave impact was applied for evaluating the horizontal impact pressure. Key quantities for the calculation, e.g. the angle between the front slope of shipping water and the structure, were evaluated by the theory of “flood waves”. Having compared with measured data, it was confirmed that the combination of these two methods is practical enough for estimating horizontal impact pressure on deck structures.

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A linear and a fully nonlinear numerical wave tanks (NWTs) were applied to study wave drift force acts on a two-dimensional Lewis form body in finite depth wave flume. These NWTs are based on potential theory and the fluid and floating body motions are directly simulated in time domain. Boundary value problems both on the velocity potential φ and its time derivative ∂φ/∂t are solved at each time step. The coupling condition between fluid and floating body is imposed as the implicit boundary condition of ∂φ/∂t on wetted body surface. The radiation condition at both tank ends are satisfied by artificial damping technique. Using these NWTs, effects of the floor step of the flume on wave drift force were studied. Measurement of wave drift force was also conducted in our two dimensional wave flume. In this report, the results of simulations and measurements are presented and the effect of the floor step on wave drift force is discussed.

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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 confirmed by comparing the directional wave spectrum estimated from the measured ship motions of a model, with the ones obtained from the direct measurement of waves in the Marine Dynamic Basin of NRIFE (National Research Institute of Fisheries Engineering).

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The knowledge of ocean waves is important not only for the design of floating structures but also for the improvement of the operation safety and efficiency of those structures. In this paper an evaluation of the conventional marine radar to measure ocean waves is done through numerical simulations. The radar system is simulated to create a typical PPI image with sea clutter information from a given ocean surface. In the simulation case shown here a simple empirical model of the radar cross-section (reflection coefficient) is used. The ocean surface patch used in the simulations was generated from a theoretical multi-directional power spectrum density distribution. In the literature many works that are able to extract the predominant direction of propagation of the ocean surface waves and the wavelength through direct two-dimensional spectral analysis of the PPI image are available. In this paper, the basic evaluation of the use of marine radar as a wave measurement device (marine wave radar) is done. Furthermore, using a simple model for the radar cross-section, this work attempts to retrieve from the PPI image the original multi-directional power spectrum used to create it.

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We had already reported the results of the Short-Term-Directional-Wave-Buoy. But there was a problem on the directional data. In another words, there was time drifting problem on the directional sensor. Since we have had this problem, we correct the buoy-coordinate-system-based data to the data based on space coordinate system by using the wind-vane on buoy itself. Then by measuring the wind direction, we could estimate the buoy direction.
This time, with solving the directional sensor problem, correction of measured time history by using measured buoy direction was done, and the improvement of Short-Term-Directional-Wave-Buoy has been confirmed through the numerical simulation, tank experiment and reliable field data were obtained.

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The authors have developed a structural mathematical model in a series of papers, that is deduced theoretically from the model of simplified vortex systems with ring vortex, horse-shoe vortex and cross-flow vortex. This model describes the ship hydrodynamic forces X, Y and N acting on a hull in turning motion, with small to large drift angles using the “component type” mathematical model.
The new model is able to estimate the forces in a larger drift angle 3090 degrees, and even in turning motion, by analyzing the hydrodynamic data of oblique towing motion with small drift angle 030 degrees. This paper presents a more accurate mathematical model for practical use, with simple empirical corrections of the previous model.

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Accurate estimation of hydrodynamic forces acting on a ship hull is essential for the evaluation of ship maneuverability.
In the present paper, the Navier-Stokes code NEPTUNE developed at Ship Research Institute has been extended to compute flows around a ship with/without a rudder in a maneuvering motion.
Brief description of the numerical method is given followed by the comparisons of the computational results with experimental values.
Since both the hydrodynamic forces and the wake flow fields show good agreement between the simulations and the measurements, the practical usefulness of the present method has been demonstrated.

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A small planing craft that has V-shape hull and hard-chine is good for running in a little rough sea at high speed. But it has been known to have various motion instabilities. From these, we may choose so-called corkscrew motion, which was supposed to include roll oscillations (chine walking) mainly and heave oscillations (porpoising) partly at high speed turning, as one of the most difficult problems to predict its occurrence at design stage and one of the most serious problems for safety. If it happens, the driver is hard to maintain his position due to large lateral acceleration and may lose craft control. This report shows that this turning instability at high speed comes from vertical dynamic instability at heeled attitude at turning, and proposes some criteria that are useful to design a new boat that has enough turning stability. These criteria are obtained from the turning motion simulation program that is newly developed as a design tool, which can judge the degree of turning stability at early design stage. Adding extra keel to hull bottom is a very effective measure for turning stability. Though its effect has been known from experience but it has been confirmed quantitatively by this simulation for the first time.

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As the Phase II project of “Research & Development of Huge Floating Offshore Platform” carried out by the Mega-Float Technological Association, the proto-type of floating airport using the large floating platform (1000m in length, maximum 120m in breadth and 3m in depth) was installed at the Tokyo Bay in 1999. The model of floating airport consists of mainly 3 floating units with runway such as A, B and C. They were constructed at different shipping yards and connected together on the sea. A and C unit for runway have been constructed at shipping yard in the Ise Bay and B unit has been done in the Tokyo Bay.
There are very few data concerning the full-scale measurement of such a flat structure with small depth. However, there is a possibility of the occurrence of various kinds of structures in the future for the development of the ocean space utilization. Transportation by towing has been one of the conventional way of techniques from old times, the limitation of experiment however exists because of its big size. The accumulation of full-scale data is quite important especially in the long distance towing of huge floating structure like Mega-Float unit in the outer ocean.
Authors made a full-scale measurement using the floating unit (100m in length, 60m in breadth and 2m in depth) in the phase I project as well as the model experiment in the basin. The towing force and strain on the upper-deck etc. have been measured in both experiments. A floating unit constructed in the phase II project is the same size as the completed structure in the phase I project. The towing force and structural strength of the floating unit have been discussed in this paper.

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It is necessary to estimate slowly varying drift forces on very large floating structures (VLFS) for their safety. The aim of our research is to develop an estimation method of such forces on VLFS in the real seas, i.e. in multidirectional irregular waves. We knew such a method for rigid bodies, but it seems to be complicated to extend the method for VLFS directly because of their hydroelastic behavior. Thus, in the previous report, we presented an easy but legitimate estimation method in which we can evaluate slowly varying drift forces by means of the integration of the squared relative wave height and also we validated our method with model tests in long crested irregular waves. In this 2nd report, we carried out a numerical calculation with various flexural rigidities of VLFS, incident angles, and incident wave periods to validate our method more generally. We also validated our method with model tests in short crested irregular waves so that we can demonstrate our method can be applied for VLFS in multidirectional irregular waves.

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Water wave diffraction by an array of plates rigidly fixed on shallow water is analysed under the assumptions of linear long wave theory. The plates are identical and equally spaced along the array. The breadth of each plate is infinitely long. Near-resonant modes occur between adjacent plates in oblique waves at critical wavenumbers and cause large pressure acting on each plate. This paper shows the relationship between this near-resonant phenomenon and an eigenvalue problem of the water wave diffraction. The result leads out that near-resonant phenomena occur when transmitted wave amplitude takes its maximum and when reflected wave vanishes. There are resonant zones, in which near-resonant phenomena occur concentratedly in the response amplitude operator. The resonant zone is independent of the number of plates and depends on the spacing of plates, wavenumber and incidence angle. The resonant zone becomes narrow as wavenumber increases, and becomes wide as the spacing of plates increases. Each resonant zone has n-1 near-resonant curves which represent the relationships between the incidence angles and the near-resonant wavenumbers, where n is the number of plates. The near-resonant curve for the largest incidence angle suggests the existence of a critical angle of near-resonance for each wavenumber in this wave diffraction problem.

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Through the recent researches on hydroelastic responses of Very Large Floating Structures (VLFSs), it has been found that the wave-induced elastic responses of a simple mat-like VLFS of homogeneous rigidity are quite larger than anticipated. Because of this fact, if a VLFS is to be used such purposes as a floating airport, certain measures should be employed in order to attenuate the elastic responses. The objective of the present study is to optimize the geometry, rigidity and other things of a VLFS in such a way that the elastic responses are minimized.
As a first report, a comprehensive parametric study is conducted on the wave-induced elastic responses of VLFSs while varying their geometries, rigidity and supporting columns as the parameters and the possibilities of the reduction of elastic responses are investigated.

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Ocean sequestration of the captured CO₂ from fossil fuel burning is a possible option to mitigate the increase of CO₂ concentration in the atmosphere. It can isolate huge amount of CO₂ from the atmosphere for long time in relatively low cost, if it is acceptable from the viewpoint of the oceanic environmental impact. The dissolution type treated in this paper is based on the idea that CO₂ dissolved and sufficiently diluted in seawater does no more harms than slightly increasing the concentration of CO₂ already contained in the seawater. The concept of CO₂ dispersion in the ocean depths by ship is a promising implementation for the efficient dilution. That is, liquefied CO₂ is delivered by ship to the site and injected into ocean depths of 1, 000 to 2, 500m with a suspended and towed pipe by a slowly moving ship. The constant movement of releasing point of CO₂ causes no stagnation and accumulation of CO₂ in seawater. The released CO₂ will form plenty of droplets, and then they rise gently due to the buoyancy, while reducing in the size to disappear by dissolution in the ambient seawater. Since the turbulent diffusion in the intermediate ocean is dominant horizontally, use of the vertical journey of CO₂ droplets will be very effective for the initial dilution. Thus, authors have good prospects for the dilution ratio of one to a hundred thousands in a couple of hours after injection on an engineering realistic scale, by means that the initial size of droplets is controlled. Drop formations from a fixed nozzle are investigated referring the common knowledge on textbooks. And the possibility of generating relatively large size of droplets from a moving nozzle is experimentally studied. As a result, it is found that the horizontal nozzle towed by the slowly moving ship is promising for the control of the drop formations in a realistic scale.

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The behaviour of the two-dimensional gravity current in an oscillatory flow is investigated by computation when homogeneous fluid and another fluid of slightly different density were released in a sinusoidally oscillating flow. The incompressible Navier-Stokes equation for an inhomogeneous fluid and the transport equation for solute were solved by the finite volume method developed in the previous paper and extended by incorporating the oscillatory ambient flow with the implementation of the unsteady inflow and outflow boundary conditions.
The results indicate that since the tail wind pushes the head forward further than the head wind brings it backward, the mean speed of the current front increases in oscillatory ambient flows. The change of the ambient flow direction makes the front distorted remarkably and enforces the instability of the density interface at some KC numbers. This instability causes the roll up of the interface and the vortex shedding from the head, both of which increase the entrainment rate in low Froude numbers. It is found that the unsteady boundary layer along the wall affects the inner structure of the current head according to oscillatory flows.

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The Superconvergent Patch Recovery (SPR) method is used to recover the Cauchy stress in large deformation problem. For mesh consisting bilinear quadrilateral elements, the validity and necessity of using the integration points of 2 × 2 Gauss-Legendre product rule as sampling points are discussed, and the reason for the good performance of this procedure is investigated. To compare the performance of the two procedures using superconvergent points and 2 × 2 Gauss points as sampling points respectively, hyperelasticity is selected as material model. Then the influence of the order of recovery polynomial to the performance of recovery method is studied by comparing results of three procedures with different choice of sampling points and order of recovery polynomials.

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New shape functions for the lateral deflection of rectangular plate elements for the Idealized Structural Unit Method (ISUM) are developed. First, the collapse behaviour of rectangular plates under longitudinal and transverse thrust is studied by elastoplastic large deflection FEM and the characteristics of the collapse modes are highlighted. Based on these characteristic deflection modes, new lateral shape functions for the large ISUM elements are assumed and implemented. Comparisons with FEM results show the applicability and good accuracy of these new ISUM elements. The importance of shape functions simulating the collapse mode accurately is demonstrated by comparing the new formulation with a previous one and by examining the influence of two yield functions.

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The assessment of the safety and reliability of double hull structure under the excessive lateral pressure requires the confirmation of buckling of the skin plate panels and the post-buckling behavior of the global structure. Recent progress of the analysis tool and expanded capacity of the computer system enables to solve such complicated problems gradually. However these analysis have not been effectively applied in the actual design stage yet because the global hull structure model is too large for this kind of nonlinear analysis. In order to accurately evaluate the post buckling behavior of whole double hull structure in a practical time, the authors have developed the new assessment system by the linear FEM analysis introducing simplified plate element with equivalent stiffness of buckled panel. This system enabled the evaluation of the post buckling strength of whole hull structure in very short time, and thus, the design for optimizing the arrangement and reinforcement of structure.

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In this study, the authors have developed a software system based on influence function method using 3 D-FEM input data and 3 D-FEM result to improve prediction ability of fatigue crack growth analysis of surface cracks which initiates from root of boxing fillet welded joints of ship structures. The software system developed in this study uses the database of influence coefficients, K_ij, developed by one of the authors, Shiratori, for various types of surface crack through a series of FE-analyses. It is shown that crack growth result based on influence function method using 3 D-FEM result is more accurate for experimental data than the result by a method based on linear approximation of arbitrary distributed stress. And further study, a simple approximate equation of arbitrary distributed stress in the cross section of virtual crack surface are determined to simplify crack growth analysis based on influence function method. Surface crack growth analysis based on influence function method using the approximate equation gives almost the same result of that based on influence function method using 3 D FEM result.

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In the fatigue strength analysis of a ship, it is most important to estimate the accurate stress fluctuation of a certain structural member of the ship in waves. In case the fatigue strength of the structural member is evaluated by the cumulative fatigue damage factor, it is necessary to obtain the long-term probability of occurrence of the stress fluctuation, which is combined with S-N curves. For this purpose, a probabilistic approach is usually adopted, and it is essential to calculate the frequency response function of stress accurately in the probabilistic approach.
As for the transverse strength of a ship in waves, hydrodynamic sea pressure in wave is the most important external load, particularly for fatigue strength of a ship. In order to obtain the stress response function caused by the sea pressure, a finite element analysis is necessary to be carried out in every wave condition in principle, because the distribution pattern of sea pressure, as well as the magnitude, along ship' s hull varies according to the wave conditions, and a non-linearity due to the free surface elevation along the side shell plays an important role. However, it may not be possible to conduct this kind of structural analysis in the structural design stage, because it requires enormous time and effort in computation.
In the present paper, the stress response function and the long-term probability of occurrence of stress caused by wave pressure are calculated with the use of the most exact method at present. The treatment of the non-linearity due to the free surface elevation along the side shell will be investigated in this process. Then, simplified methods to predict the stress response function and the long-term probability of occurrence of stress are proposed. Comparing these calculated results by the exact method, approximate method and conventional method, the accuracy of the prediction method is discussed from the viewpoint of the design tool for fatigue strength of a ship.

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This study is the second report concerned with statistical analysis on long-term distribution of wave induced load. In the first report, authors examined which factor gives influence by load revel in the long -term distribution, such as significant wave height, average wave period of supposed wave condition and relative angle between ship course and wave direction. The long-term distribution was decomposed into every these factors and a contribution rate analysis method for these factors in each load revel was introduced. Based on the method, it was clarified that the maximum wave induced stress value in the vicinity of the probability of exceedance around 10-8 can be governed by the most sever short-term wave condition which has the largest value of short-term wave induced Raleigh distribution parameter.
In this report, the shape of the long-term distribution of the wave induced load for evaluation of fatigue strength is studied. Based on S-N curves and Miner's rule, the relation between the fatigue damage and supposed wave condition to calculate the long-term distribution is examined. The contribution rate analysis method for fatigue damage from supposed wave condition, such as significant wave height, average wave period of supposed wave condition and relative angle between ship course and wave direction, is introduced. It is shown that the most sever short-term wave condition, defined by the former report, also plays the most important role in the fatigue damage. The simple estimation method for long-term distribution described by Weibull distribution from the statistical propaty of the most sever short-term wave condition is introduced. Several examples show the applicability of the estimation method and estimation errors of the maximum value with probability exceedance 10^-8 are less than 5% and of the fatigue damage rates are within 1030% large value.

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The present study has been carried out under the Mega-float Project as one for developing an accurate general-purpose three-dimensional computer program for hydroelastic responses of Very Large Floating Structures (VLFSs) due to wave action in water area with complicated geometry close to the real situation.
In the first report, a versatile and powerful approach for wave hydrodynamic loading was newly presented, based on a hybrid finite/infinite element formulation of domain decomposition type, and test calculations gave good results coincident with the existing measured and calculated ones.
The present paper describes, in detail, such computational improvements and programming techniques adopted in the computer program to enhance its computability to the resulting large-scale models, as 1) the utmost reduction of the localized computational domain, 2) the application of domain decomposition algorithm, composed of the introduction of hybrid prism elements with the domain-wise vertical orthogonal eigenfunction expansions, and planar finite elements, and simple and flexible particular solutions corresponding to arbitrary bottom motions of VLFS, 3) the use of the hierarchical finite element technique based on super-elements with hundreds of nodes, formed numerically from blocks of the hybrid elements through the static condensation technique, 4) the final symmetric and block-banded coefficient matrix derived by the introduction of hybrid infinite elements and the proper renumbering and matching of condensed unknowns on an inner fictitious interface. Then, analytical explanation to each implementation have been presented.
Additional test calculations have been conducted for a 1200 m model VLFS, changing the terms of vertical eigenfunction expansions, the mesh size, and the location and configuration of the outer fictitious boundary, which have clarified the contribution of each factor to the numerical results.
Pilot calculations for a VLFS with partially variable rigidity and the one with L-shaped water plane have been successfully done, thus illustrating the potential of the present methodology.

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When carrying out stress analyses of a Mega-Float structure subject to wave loads, it is in many cases difficult to make an all-in-one program containing both of hydroelastic analysis and stress analysis because of capacity and processing time of computers. To cover such situation, a practical two-step method is proposed in which separately obtained first step output of hydroelastic analysis is given to the second step of stress analysis, where the static analysis program for Mega-Float is used.
The stress analysis is done for each of the real part and the imaginary part of the hydroelastic solution to obtain two typical simultaneous set of stresses, and then, calculations of amplitude distributions for experienced maximum stresses while waves pass are done using the two parts.
The method is applicable to plane grillage models and also three-dimensional finite element models based on common skeleton consisting of the lines of longitudinal and transverse bulkheads and girders. Hence, flexible application can be done according to various stages of design work.
Results of trial analysis are shown for the cases of head sea and diagonal sea applied to the grillage model and the finite element model. From those results, it has been found that the method proposed here can be used as a useful analytical tool for structural design of Mega-Float.

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The hydroelastic response analysis of a mega-float structure in waves is usually made by integrating its structure model and fluid model, but usually the analysis model become a very large one. It is, therefore, difficult from the aspect of calculation time limitation to make such an analysis by exactly incorporating the structurally discontinuous parts such as girders with large openings in a mega-float into the above structure model.
On the other hand, since the mega-float structure has many structurally discontinuous parts, it is very important to establish an evaluation method of the stresses caused by the hydroelastic response at such parts.
In these circumstances, noticing the fact that wave-exciting forces acting on the mega-float are concentrated at the end of the wave incident side, the authors have invented such a stress analysis method of mega-float structurally discontinuous parts (girders with openings, etc.) as is mentioned below and verified its propriety by actual application of it. The method is that a mega-float structure is replaced by an FEM vibration model of a 3-dimensional slip-shaped girder supported by a buoyancy spring which is excited at the end of the wave incident side in the vertical direction and the vibration response analysis is carried out.

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Very Large Floating Structure (VLFS : MEGA FLOAT) of several thousand meters long are being considered for various applications such as floating airplanes and so on. The MEGA FLOAT recently designed as a thin mat-like configuration and very large horizontal area. Therefore this type of structure is very flexible and the elastic deformation due to wave forces is more critical than the rigid body motions.
Recent investigation of hydro-elastic response analysis of MEGA FLOAT have been much improved, the behavior of structural body induced by the wave force have been cleared.
From those results of hydro-elastic response analysis, global and generous stress distribution have been able to estimated, however detail analysis can not be estimated directly because it is difficult to solve full scale structural model. Since there are many discontinuous and stress concentrated positions in the structure of multi-purpose MEGA FLOAT, we proposed the detail structure by using phase structural analysis method applied the results of hydro-elastic response analysis to the detail local structure.
This paper introduce one of the orthodox methods of the phase structural analysis method by the zooming technique of FEM structural analysis. We show the calculation method for the structural zooming model which is applied to the forces from the hydro-elastic response analysis, and the results and consideration for the few examples of the detail structure of MEGA FLOAT.

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Nickel ore is natural clay containing large lumps. Every year, around four million tons of this material is transported to Japan from Indonesia, New Caledonia and Philippine by bulk carriers of around twenty thousands to forty thousands tons dead weight tonnage. When nickel ore contains much moisture, slopes of its cargo piles in cargo holds may slide, because its shear strength is low.
To prevent sliding failure of a bulk cargo, it is necessary to evaluate the shear strength of the cargo prior to shipment. Shear strength of nickel ore can be measured by direct shear tests or triaxial compression tests in a laboratory, and the stability of the cargo pile can be evaluated by slope stability calculation which is utilized in the field of soil mechanics based on the measured shear strength. Such method for evaluation, however, cannot be conducted at the time of shipment of nickel ore, because it takes at least a few days. Taking these issues into consideration, we developed a new in-situ test procedure for evaluating shear strength of nickel ore which can be conducted at places of loading for nickel ore in a few hours in view of prevention of sliding failure. To develop the criterion for judgment on sliding failure of nickel ore, we carried out direct shear tests and slope stability calculations for nickel ore from five ports.
The new test procedure mainly consists of three steps, i.e., removal of large particles, insertion of the sample in the mould and cone penetration test. First, particles larger than 19 mm are removed from the wet sample by passing through an appropriate sieve. Next, the sample is inserted in the mould and compacted to make a consistent specimen. Then the cone is pushed down into the specimen and the maximum value of reaction force is measured. When the force is less than 300 N, the nickel ore should not be accepted for loading without taking special safety measures.

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This paper describes about the method for fair surface generation in ship hullform design aiming at the automatization of surface fairing. It generates an approximating surface from section curves according to the distribution of curvature. The generated surface has dense parameters in high curvature areas, and sparse parameters in low curvature areas. This method has three advantages de-scribed below. First, it can suppress the distortions generated by traditional methods. Second, it can use additional curves that cannot be used in traditional skinning methods. Finally, it can do surface fairing efficiently without the great loss of geometric feature.

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The effective planning of production control in the shipyard is greatly depended upon the accumulated personal knowledge and know-how of the well-experienced and qualified planning engineers.
However, it is also understood that it is quite difficult to draw out and disclose such extensive knowledge and know-how and procedure in their mind, completely.
To establish the effective system of production control under such circumstances, it was tried to categorize the full process of production control into two parts. i. e., one is the part closely related to the well-experienced engineers' knowledge and know-how and the other is the part to be carried out by the computer simulation.
After that, the both parts to be composed into the unified system.
It is most practical and effective that the planning will be planned by the well experienced engineers' knowledge at the initial stage of production control and thereafter the simulation to be performed by computer.
Further, by introducing the knowledge and know-how of the well-experienced planning engineers into the system as much extent, the effective planning of production control can be prepared even by the unexperienced staff.
In this paper, the following three major items from our study to be reported for such purpose. i. e.,
(1) Evaluation method of dividing hull into blocks.
(2) Production control by well-experienced engineers and computer.
(3) The procedure of work leveling and evaluation at the middle stage of production control planning.

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Usually, watch team is composed of two or well trained persons. For the future, domestic shipping industry will be short of crew resources But it takes a long times to educate watch keeping practice for crews. Herewith, we could achieve one person bridge operation (OPBO) systems more safely and comfortably compared to traditional dual watch system, then we could sustain activities in domestic industry and manage to trade off reasonable safety and productivity. For this purposes, we have developped the system which has ability of more than dual persons, and demonstrated OPBO system on board which is physically and mentally comfortable. The main human machine interface is in usage of the voice control input/output equipment. This paper writes the OPBO system in brief and evaluates the results of physical and mental aspect during sole watchkeeping and.also analyzees the performance of some sole and dual persons' watchkeeping standards.

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The Northern Sea Route (NSR) shall keep its advantages in costs against other alternative transportation means including railways or routes through the Suez Canal. INSROP Phase II are assigned tasks to perform a ship transit simulation in order to answer concerns about the cost benefit and associated risks in case of utilizing the NSR commercially. In order to conduct the simulation; keeping with some confidences, multi disciplinary knowledge is necessary. Thus, Simulation of Ship Navigation project is divided into nine work packages (WPs) and our WP8 takes the responsibility of integrating other project results.
Chapter 1 describes introduction and background. Chapter 2 summarizes the conditions utilized in this simulation. Chapter 3 and 4 describe the computer code developed for this simulation. In this simulation, an effort is made to connect the ship velocity simulation code by WP6 and the ice conditions presented by WP2. The concept for the Ice Index originally introduced by the Arctic Ship Pollution Prevention Regulations (ASPPR) as ice numerals is modified to express the ice conditions quantitatively as a solution, then the probabilistic relations between the ice condition and ship velocity are developed. This method considerably enables shortening of the simulation time with keeping rational relation between the ice condition and transit time. Chapter 5 summarizes the results. The simulation was performed in twofold. One is the simulation named Monthly Voyage Simulation (MVS) representing the required cost on each month. MVS is the most preferable method to look at the general trends for the variations for transit times by season and sea area, and icebreaker escort times etc. The other is the simulation named Annual Serial Voyage Simulation (ASVS). ASVS aims to estimate a number of voyages per year and evaluated freight cost per voyage as /ton. ASVS is widely used by the shipping industries to judge feasibility in terms of cost and profit. Final chapter describes conclusion and recommendation from the study. The capital cost and icebreaker tariff have significant effects among the cost parameters. The tariff rate of 4.0/GT seems to make the NSR economically feasible under the condition that the performance in open water of ice-breaking bulk cargo is improved. The Ice Index will be a good index to quantitatively express the difficulty of the navigation in the NSR.

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Sacrificial specimen is a small sized fatigue specimen which is designed so that fatigue damage may be produced in the specimen sufficiently earlier than in a structural member when it is secured onto the structural member. The purpose is to make a diagnosis of structural safety based on the monitoring result of sacrificial specimen. In the previous study, a sacrificial specimen was developed for the purpose of fatigue life prediction of structural members. In this study, a high-sensitivity sacrificial specimen is developed for the purpose of estimating the characteristics of long-term stress distribution working on structural members. In order to increase the fatigue sensitivity, a mechanism to amplify the member stress is newly applied. The sacrificial specimen is cemented onto a smooth specimen, and fatigue tests are carried out under constant stress amplitude and block loading. It is found that new sacrificial specimen can amplify the member stress appropriately and shows stable fatigue property. Further, the sacrificial specimen is applied to a structural member of actual ship. Stress monitoring is carried out during the period of fourteen months under the service condition. At the same time, stress measurement by strain gage is conducted near the sacrificial specimen. It is found that the characteristics of long-term stress distribution estimated by sacrificial specimen agrees well with that of strain gage.

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It is sometimes reported that the heated tank structures in engine room are suffered from serious vibration, in particular fuel oil service tank or fuel oil settling tank. That phenomenon is quite strange, since the tank structure is designed so as to avoid resonance with exciting forces. However the reason of that resonance has not always been clarified in many cases.
Heavy vibration of tank panels occurred in a heavy fuel oil settling tank in VLCC. The tank panels vibrated at 6.30Hz to 7.12Hz frequencies with 1.13mm of maximum single amplitude, although the natural frequency of tank panel had been designed to be more than 23.3Hz. The reason of the vibration is investigated on the basis of theoretical analysis and FEM analysis, consequently following facts are clarified :
1) In case of multi-tiered of tanks, oscillation of adjacent tank panels, in particular upper and lower panels, caused the pressure increase due to interference. That pressure reduced the natural frequency of panel due to the increased added mass of fluid.
2) The thermal stress due to the tank heating caused compressive stress in tank panel, since the extension of tank structure was restricted by engine flats, transverse and longitudinal bulkheads of normal temperature. The compressive stress reduced the natural frequency of tank panel.
3) The combination of the above two factors decreased natural frequency of tank panel to 1/4 of the original one and induced the resonance between the reduced natural frequency and the exciting frequency of main engine.
This investigation can provide the designers helpful suggestions to avoid the vibration problem of multi-tiered and heated tank structures.

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In order to automate the line heating process, heat transfer between flame and plate has to be solved theoretically. However, there is no close calculation and experiment in the high temperature and velocity flow field such as line heating process, and above heat transfer has not been clarified yet.
The aim of this study, as the first step to analyze heat flux between gas and plate, is to clarify the heat transfer and heat conduction in combustion flow field from nozzle exit to plate surface during spot heating. 3-dimensional computer code for calculating combustion and flow of gases is developed.
Using this code, impinging turbulent gas jet flame and flow field are closely analyzed. Heat conduction into the plate and heat transfer between plate and low-temperature gas at the back of plate have strong effect on the flow field. These heat transfer phenomena at the steel plate is also considered.

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Recently, Japan has become a nation of old people, and also shipbuilding industries are not exceptional. To increase productivity and to keep safety and health of the workers in such circumstance, the current production system must be reviewed so that it will be suitable to human oriented production.
Developments of biomechanics and ergonomics, together with the computer simulation technique, help to establish a virtual ergofactory which combines productivity and humanity well.
This report has picked up the welding work, which is the typical job in shipbuilding, as an example of human task simulation; the static strength prediction on human body and low back compression analysis.
As a result, the torque and/or forces on segments and joints in a human body were calculated in accordance with the each working posture, and these showed that the welder would suffer from severe torque on the knee and pressure on low back at usual squat posture (flat position).

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The authors pointed out in the previous paper that it may be possible to understand / evaluate the psychological situation under stressed conditions analyzing facial expressions and feelings of subjects exposed to low-frequency oscillations.
The present paper deals with the objective measurements, analyses and evaluation of emotional and psychological situation from analyses of facial expressions deliberately expressed by subjects. They added blinks for taking the dynamic changes of facial expressions into account.
The method of discriminant analysis was applied to extract dominant parameters, and then the linear multiple regression analysis was applied to evaluate and estimate the relations between psychological situations and facial expressions.
Though the number of experiments is not many, they obtained results that psychological situation may be estimated from facial expressions with relatively high possibilities.

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