Micro-genetic algorithm has been applied incorporating boundary element analysis to the optimal design of lifting bodies, i.e., hydrofoil, propeller etc. In case of hydrofoil, the 2-dimensional section with NACA 66 (mod.) thickness distribution and NACA a=0.8 camber distribution are fitted with B-spline polygon vertices. Then the change in shape of the 2-D section is made by shifting B-spline polygon vertices vertically. Using this generated section, trapezoidal hydrofoil is analyzed by 3-D boundary element method. GA then updates the section shape by shifting polygon vertices and finally finds the optimum section, for which, hydrofoil attains highest L/D ratio satisfying some imposed constraints. In case of propeller, chord, pitch, maximum thickness and camber ratios are also fitted with B-spline. The variations in the distributions are made by shifting B-spline polygon vertices, and improved propeller of highest efficiency is found by GA satisfying some design constraints. In this study, μGA is found useful and prospective tool for the optimization of lifting bodies incorporating analysis method because of its faster convergence.

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Frictional resistance of a prismatic model at high advanced speed is measured for four trim angles, and compared with one for a flat plate. The measured frictional resistance coefficients are higher than Schoenherr line, and depend on trim angle and R_e. The flow on the bottom of model is estimated by the flow around a corner, and the fiictional resistances for uniform flow and accelerated flow are calculated by the boundaly layer theory. The difference of both calculated frictional resistances is small. The high frictional resistance occurs on the high average flow on the bottom.

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There have been papers about improvement of the ship performance by the representative ships, for exarmples, the IDEMITSU-MARU, the TOKYO-MARU, etc. There are, however, few papers about ship performance of the whole ships. The data of ship performance were collected since 1963 by SEMPAKUMEISAISHO, which holds all of ships registered in Japan. This paper shows the change of principal dimensions, sea speed, maximum continuous output about the collected crude oil tankers. Analysis results for ship performance are shown with some assumptions. The resuits show that the larger the ships was, the better the propulsive performance was and it is found mainly because of smaller viscous resistance by larger Reynolds Numbers. The results show that the ships, which are built recently, have better performance.

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This paper presents a fundamental research on the free surface flows near a two-dimensional transom stern by flow visualization tests and CFD analysis. The flow visualization tests were conducted at a small circulating water channel with a two-dimensional ship model and the argon laser sheet light. The computational approach is based on Reynolds-averaged Navier-Stokes' equations considering free surface flow. As a consequence, it was found that the free surface flows near the transom stern were complex and comprised by the interaction between vortex shedding from the stern end and free surface.

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Minimum resistance is one of the most important factors in hull from design. Traditionally, hull from design is dependant upon the skills of highly experienced naval architects. If a completed optimization method of hull design with minimum resistance could be developed, design time would be shorted dramatically and this method would help the naval architect who doesn't have much experience. Recently, some optimization methods using CFD for minimum resistance have been developed. However these methods need long computation time. In the practical design stage, a design time is needed. So we aim to develop an optimization method requiring less time. In this paper, we focus on the optimization of hull form design for minimization of viscous resistance. Viscous resistance takes the greater part of resistance in full hull from (for example VLCC, Bulk Carrier etc. ) So, reducing viscous resistance is very important in designing full hull from. The object of our optimization method is to achieve a hull from with minimum viscous resistance. Our optimization method consists of Nonlinear Programming, Deformation method for hull form, and Prediction method for viscous resistance that can predict the form factor quickly. Our method optimizes in a frame lime for minimum viscous resistance and can obtain results for short time (about 4〜6 hours on PC.) This method directly optimizes the hull from. The result of this optimization is shown in this paper. And we verified the results by comparing with the resistance test in NKK TSU SHIP MODEL BASIN.

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The hull form optimization has been recognized as one of the most important application fields of wave making resistance theories, and many related research works have been done. In near future, designers will be able to determine the hull form by using the optimization method based on advanced numerical ship hydrodynamics and nonlinear optimization programming techniques. In the present paper, the hull from optimization method based on Rankine source panel method and Sequential Quadratic Programming (SQP) technique is discussed. In the optimization process, the initial hull form can be improved by changing its frame lines and bow stem profies under the prescribed design constraints. Especially, shape optimizations of bow bulbs are shown for non-protruding and protruding bow bulb. As numerical examples, a fishing vessel with non-protruding bulb and the HTC (Hamburg Test Case) container ship with protruding bulb are selected.

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The fuel saving device "Super Stream Duct" was developed in 1989 using Hitachi Zosen's original technological knowledge, and it's fuel saving effect has been confirmed through a large number of model tests and sea trials. Almost every large full body ships built by Hitacihi Zosen have been equipped with SSD. In this study, we try to simulate the flow field around the ship equipped with SSD, and investigate it's hydrodynamic effects on the propulsive performance by CFD applying the overlaid grid method to NICE-code. Firstly, in order to examine availability of the overlaid grid method, we estimate the rudder drag by this method and compare with that of the single grid method and model tests, We confirm that the accuracy of estimated thrust at the leading edge and the rudder drag by this method is remarkably improved. Next, we apply this overland grid method to SSD together with the rudder. The estimated effects of SSD on the wake distribution at propeller position, the viscous resistance (form factor K) and selfpropulsion coefficients (1-Wt, 1-t) show good agreements with results of model tests. Then we make some considerations on the mechanism of improved effects of SSD on the propulsive performance.

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A slender planning ship theory without gravitational effect was proposed from a viewpoint of perturbation method. A asymptotic expansions of velocity potential near the hard chine of rectangular planing plate were constructed in both domains near and local near field. In the local near field, there was a self-similar flow along the hard chine and it showed that existance of homogeneous solution in the local flow field near the hard chine. The homogeneous solution was essential to represent this local near field where non-linear wave generated and it was identified to impose Kutta's condition strictly on the hard chine. This local flow field was solved to identify the homogeneous solution on the assumption that the non-linear wave was so small. and the result was compared with the Savitsky's formula which was derived from experimental data qualitatively. Some numerical methods to solve this local flow field were suggested and the subjects for numerical computations were pointed out.

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Steady wave forces and moment at rest are important to estimate drifting motion of a ship in waves or to estimate manoeuvrability of a ship in waves at low speed. However, it is difficult to measure these kinds of forces and moment without disturbing six degrees of ship motions in waves. Restraining free ship motions during measurement distorts property of steady wave forces and moment. That is one of reasons why not so many experimental data consisting of surge and sway forces and yaw moment have been reported so far. Experiment for measuring steady wave forces and moment at zero forward speed are carried out using a newly developed measuring system. This measuring system uses three torque motors which play two roles, one is as weak springs to produce restoring forces for surge, sway and yaw motion and the other is as counter weight for balancing steady wave forces and moment. Using this mechanism, one can easily attenuate spring constants and counter forces and moment by setting continuous electrical signal and make a model ship remain in designated area during measurement without much affecting six degrees of free ship motions of wave period. Calculations based on 3-D panel method and Strip method are provided for evaluating experimental data including ship motion of wave period and steady wave forces and moment. Calculated values for ship motions well describe experimental data. Therefore this measuring system is considered not to restrain model ship motions of wave period during measurement. One of calculations for surge and sway forces shows fairly good agreement with experimental data. Some discussions about differences between experimental data and calculations for yaw moment and also about reliability of experimental data for steady wave forces and moment are provided.

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Much wave energy exist in the ocean. If we could succeed to extract the energy from the ocean, the energy saving effect is large. It is known that the anti-pitching fins reduce ship motions and the bow wings also generate the thrust caused by the vertical velocity of ship motion, wave motions and her advance velocity. To design the bow wing, we evaluate the effect of tapered and sweepback wing and the interference between ship and wings. By experimental and theoretical study in regular and irregular waves, we make sure the bow wings reduce the ship motions and resistance in waves. However, the bow wings have a weak point to be damaged by the slamming in rough sea. Then the procedure to estimate the effective conditions to operate the bow wings is investigated.

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Model tests in head seas were carried out in order to develop an estimation method of relative water height at stem in rough seas. The effect of wave beight on ship motion and on relative water height at stem was discussed as follows. (1) Ship motion can be estimated accurately taking account of nonlinear effect of hull shape. (2) For the estimation of relative water height at stem, it is important to take account of dynamic swell up of water surface due to wave diffraction in the direction of shdp's longitudinal axis.

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In order to clarify availability of the so-called cross-flow model, some model experiments on hull hydrodynamic derivatives due to drift angle have been carried out with segmented models. The lateral forces on each of the segments were measured for various ship hulls including a flat plate. Here, it is assumed that lateral force on each segment can be expressed by a formula consisting of linear and second order terms. The linear and nonlinear derivatives are determined from the curve-fitting by a least-squares method. This report gives experimental results of the distribution of the nonlinear lateral force component over the ship's length. A comparison is made between local values of second order derivatives and cross-flow dlag coefficients at a drift angle of 90°. As a result, it is indicated that a ratio of the two values is a function of the longitudinal location. Moreover, distribution of the ratio is greatly dependent on the ship's hull form. In predicting the nonlinear derivative with sufficient accuracy, the cross-flow drag coefficients for 90°drifting should be corrected when s ship moves obliquely. Development of prediction procedure of the correction factor is left as a futule problem.

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Regular wave diffraction problems by a sphere and spheroid with no forward velosity are simulated. The amplitudes of hydrodynamic forces are compaured to linear results. Waves arround a sphere and spheroid with forwald velosity are simulated. The hydrodynamic forces acting on it are calculated. A method to simulate linear waves is discribed for the reduction of the computational cost. Wave penetrate boundary condition is employed to simulete sinusoidal periodic waves around a body.Wave fields around a restrained sphere and a restrained slender spheroid are simulated. Simultaneously hydro dynamic forces on them are estimated. Wave field around a free heaving sphere are simulated.

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In previous paper, the upper and lower bounds of hydrodynamic force acting on a body in an infinite fluid were discussed. In case where free surface exists, the hydrodynamic force can be made as the stationary value of the functional of the variational problems, but the upper and lower bounds of the hydrodynamic force can't be obtained, since the variational problems are not minimulm or maximum problems but stationary ones. The reciprocity and action theorems are obtained as in the previous paper. Interesting theorems such as Haskind theorem which give relationships between the scattering and radiation problems can be derived.

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In experiments of water waves in a tank, reflections from the tank walls are very unfavorable. Active motion of the wave maker and tank walls may eliminate the unfavorable reflections. Generally speadking, this method, however, may be rather expensive. But, even if the experiment is conducted in this unfavorable environment, there is a method to extract the useful data from the data obtained in the unfavorable condition. Instead of removing tank wall reflections physically, a numerical elimination may be possible with the proper measurement and data processing for the purpose.

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It is well known that the coupling effect of sway on roll of a ship at zero forward speed in beam seas is significant. The effect at forward speed, however, has not been clarified yet. In this study, the coupling effect of a ship at forward speed is experimentally investigated. Roll motions of a scale model of a training ship "Kagoshima maru" running in beam seas are measured in sway-fixed condition, and the results demonstrate that the roll amplitude increases with forward speed. It is common that the roll amplitude of a ship generally decreases with forward speed since the roll damping of it increases with forward speed. Therefore the phenomenon obtained in the measurements is different from the general characteristics of roll motion of a ship. To clarify the reasons, measurements of roll damping and wave exciting moment are carried out, and the lift component in the wave exciting moment is predicted. Then, it is revealed that this is partly because the lift component created by transverse velocity in beam seas increases the roll exciting moment, and partly because the roll damping of the ship used here does not increase with forward speed. The characteristics of the roll damping of the ship are also discussed.

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Classical theories on ultimate strength of plate girders in shear/bending loading have already been employed in ISUM formulation for plate girders encountered in ship structuores. Girders in doublebottom type structures, however, may show different collapse behaviour. To clarify this behaviour and to investigate the applicability of classical theories (Basler and Fujii ), finite element analysis is used, both on plate girder specimens and on double-bottom girders. It was found that the behaviour of web panels is similar to that of plate girders, thus related assumptions on buckling and post-buckling web behaviour may be kept, or slightly changed. Conversely, the flange behaviour is totally different, since these are not isolated but parts of continuous plating of inner and outer bottom; their dimensions are also very different from those designed for actual plate girders. New assumptions are needed to estimate flange contribution in girder collapse, in every loading condition. A new idea is proposed in this paper, to improve the accuracy of ultimate bending moment estimation. FEA results also shed some light on the collapse under combined shear and bending. As a general conclusion, estimation of buckling and ultimate shear force may still employ Fujii's theory, and / or adjust it to particulars of double-bottom girders. Corresponding bending moment limit values, however, cannot be calculated with plate girder theories; as mentioned above, 'flange' behaviour is completely different, especially due to continuity of plating and its dimensions.

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Vibration guidelines for evaluation of merchant ships (ISO6954) will be revised and published shortly. New guideline has been chamged substantially because of compatibility with ISO2631 which provided evaluation of human exposure to whole-body vibration. We proposed representation formula for vibration sensitivity curve in terms of weighting function and minimum sensitivity value, to compare various evaluation methods at the same figure. Using this formula, relation between physical quantity (velocity) of present evaluation value and sensory quantity of new version was made clear. Feature of new guideline was described by comparing 13 items of both guidelines. The evaluation values calculated by both methods for 20 ships data are compared mutually and the relative position of vibration levels were investigated. Some ohservations are proposed from practicial viewpoints necessary to apply new guideline. We defined of multi-frequency coefficient and obtained its value from measured data of ships. By introducing this coefficient, simple method for estimation of vibration response corresponding to new guideline is proposed.

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This paper deals with the dynaumic response behavior of ring-like hexagonal floating structure supported by columns in regular waves, as a part of basic studies on floating artificial islands. The dynamic response behavior of a 1,000m-class structure under trial design in regular waves is numerically obtained by using framework model on an elastic foundation. Effect of the bending rigidity on the frequency response amplitude of the structure are also investigated by numerical calculations for various values of the bending rigidity. It is found from calculation results that the effect of the bending rigidity on the response amplitude of the bending moment is remarkable. On the other hand, the effect of the bending rigidity on the response amplitude of the displacement aud torsional moment is comparatively little.

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The authors proposed a FEM code for hot cracking analysis using temperature dependent interface element in the first report. It was applied to the analysis of hot cracking test under welding. Thrugh comparison with experimental results, the validity of proposed method was demonstrated. However, the stable static solution is not always guaranteed due to the strong nonlinearity of the interface elelment. To avoid this problem, static-dynamic hybrid method is developed. The proposed method is applied to tensile test of elastic and elastic-plastic plates with initial crack, It is also applied to Fish Bone type hot cracking test and the versatility of proposed method is examined. By introducing static-dynamic hybrid method, it becomes possible to analyze the entire process of crack growth from the initiation to its arrest.

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In the present study, a new prediction method of transportation demand based on a benefit-cost-risk model for users is developed, and the results are economically evaluated by a net present value and an internal rate of return for operators. The benefit-cost-risk model is deduced based on the utility theory in which users are assumed to behave like an investor in choosing a transportation system among many alternatives using the following factors, traveling fale, and time as cost, comfort, convenience, and safety as benefit, and motion sickness, and exhaustion as risk. The model assumes that the users always choose the transportation system, which has the maximum benefit-cost-risk ratio. Results by the model are compared to those by a generalized cost model that was proposed by one of the authors in the previous paper. In order to assess the present method, a feasibility study of fast passenger-car ferries in Osaka-Tokushima route is carried out. The results two models show that when routes are relatively short, fast passenger-car ferries of 40-50 knots are highly competitive with other transportation systems even with channel-bridges.

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From viewpoints of effective use of coastal sea area, many kind of very large offshore structures in the enclosed sea are planned or investigated, With this tendency, studies of the technology of environmental impact assessment became very important as well as the technology of design and construction of the offshore structules. In a marine environmental impact assessment, grasping the change of tidal current and residual flow due to the existence of the offshore structure are very important and these become necessary basic data to evaluate flow characteristics and diffusion of the pollutant, and furthermore, to assess the chamge of eco-system. The tidal current simulation using NS equations became popular and massive data of flow fields can be obtained for a very short time. In this paper, calculating methods of the tidal current and seawater exchange and their applications are discussed from standpoints of the methodology of easily understandable expression of simulation data. Namely, 1) Calculating method of a particle tracing in the tidal current by the Eulerian-Lagrangian method are investigated. And the seawater exchange and the residence time of particles around an offshore structure in Osaka bay are calculated and compared with the experimehtal results. 2) This method is applied to the tidal flow and seawater exchange around Kansai international airport (phase 2: under construction) and compared with the results of its environmental impact assessment. 3) It is shown that this method is reasonable and easy to understand environmental impact of the tidal flow.

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This paper deals with an application of image measurement called PIV (Particle Image Velocimetry) to flow field in coastal area. In order to develop a practical image measurement method in the coastal area, chlorophyll distribution is measured by means of the so-called Ocean Chlorophyll Algorithm. The images of sea water in Yura Bay, located in the southern part of Osaka Bay, are taken with digital CCD camera attached two kinds of optical filters. The chlorophyll distribution is measured and analyzed and conventional cross-correlation method is applied to measure the current. The result is compared with the path line of a buoy and with the velocity vectors calculated by CFD code.

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Flow visualization technique has been very useful to understand the physical phenomena in a flow field. Recent developments of the digital image processing produce a new measurement technique for flow velocity using visualized images. It is well known that PIV (Particle Imaging Velocimetry) is now firmly established as a powerful tool to measure the instantaneous flow velocity in an extended flow field. The so-called correlation method, one of the most popular technique in the image measurement, needs the small interrogation window of which the size should be suitable for both flow field and image quality. It also needs long consuming time for the analysis owing to the convolution integral. The wavelet transform enables to examine the image quality such as spatial frequency and to make its analysis short, applying the correlation method on the wavelet domain.

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The three-dimensional computation was carried out to investigate the mixing of stratified fluid by surface cooling. The numerical two-dimensional model developed in the preceding paper was extended to the three-dimensional cases. The incompressible Navier-Stokes equation for an inhomogeneous fluid and the transport equation of density fluctuation were solved by the finite volume method. The surface cooling was made with Dirichlet boundary conditions of constant temperature imposed at the top boundary in the model. The results show that the vertical profile of the horizontally averaged density distinguishes the mixed layer developing from the lower layer of stratification in the similar way to the two-dimensional mixing process. When the cooling starts, the three-dimensionsional and regular cell structure is formed in the thin layer adjacent to the cooling top surface, The cool and dense fluid converges into the cell wall and falls down along it. It is found that the flow pattern of the three-dimensional vertical convection may affect the rate of mixing by surface cooling.

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The unsteady behaviour of the head of the gravity current in an oscillatory flow was investigated in the laboratory. A flap was controlled in a vertically circulating tank to generate a sinusoidally oscillating flow and a gravity current along a horizontal wall. In the visualization experiment the digital image processing was applied to quantity the dye concentration in the head of the gravity current. The results show that the mean speed of the current front increases in the oscillatoly flow. The head becomes thick in the tail wind and thin in the head wind so that the tail wind pushes the head further forward than the head wind brings it backward. These results are in a good agreement with the numerical prediction reported in the preceding paper. It is confirimed that the interaction of the current with the unsteady boundary layer of the ambient flow is one of the most important mechanism for oscillating gravity currents.

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Generally, linear control theories are used in ship autopilot design. When the ship is directionally unstable and therefore nonlinear, the dynamics of the ship should be linearized approximately at its equilibrium point. This will however adversely affect its performnance in proportion to the distance between its operating point and the equilibrium point. Recently there have been many studies made relating to nonlinear control theories with favorable results. One promising result is the external linearization method. This is also referred to as the exact linearization method as differentiated from the approximate linearization method. As described in this paper, we have applied the exact linearization method proposed by Ishidori to the 2nd degree of Freedom Control with path planning and MRAS (Model Reference Adaptive System) and have evaluated its effects by numerical simulation. It is found that when 2nd degree Freedom Control with path planning is applied during fast course alterations, compensation must take into consideration transient response in addition to the nonlinear steady turning characteristics of the ship. An improved design method for the feed-forward controller is also proposed. Further, the affects of ship nonlinear directional instability on the adaptability of MRAS were also studied and it was demonstrated that the MRAS provides adequate adaptability under such conditions.

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