This paper is the first half of the report on the study on microbubbles carried out by the SR239 project of the Shipbuilding Research Association of Japan, and describes the preparatory study for the full-scale experiment using a 116m-long ship. In the present study, first the skin friction reduction effect by microbubbles was investigated including the use of an array-of-holes plate for bubble generation, the effects of streamwise pressure gradient, surface curvature, and vertical plate, the sea-water effect, and the effect of bubble size. Bubble generators for the full-scale experiment were designed and built, and a preliminary injection experiment was carried out. Two new measuring devices for the full-scale experiment were developed; they are skin friction sensors and local void ratio sensors. Microbubble experiments were carried out in a 400m-long towing tank using a 50m-long flat plate ship, in order to obtain the scale effect data and to confirm the validity of the new devices for the full-scale experiment. The use of adhesives to fix measurement devices and cables on the hull surface was tested and established. The hydrodynamic fairing of the cables was also tested and established. Finally, a preliminary microbubble experiment using a small ship was carried out and the bubble behavior was observed.

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This paper is the second half of the report on the study on microbubbles carried out by the SR239 project of the Shipbuilding Research Association of Japan, and describes the full-scale experiment using “SEIUN MARU”, a 116m-long training ship that belongs to the Institute for Sea Training. Using numerical analysis and the experimental data obtained in the preparatory study described in the first half of the report, the net energy saving of SEIUN MARU by microbubbles at 14kts was estimated to be 2%. In the full-scale experiment, the trajectory of the generated bubbles was observed using underwater TV cameras and was found to shift more upward than predicted. The local skin friction was measured at several locations on the hull surface, and the skin friction increase as well as decrease by the bubbles was measured. The local void ratio was measured at one point on the hull surface, and the bubbles were found to travel slightly away from the hull surface. The change of the ship speed and shaft horsepower by microbubbles was measured, and the decrease or increase of engine power at constant ship speed was analyzed. In the most cases of the experiment the ship speed decreased by the bubble injection, mainly due to the increase of ship resistance and the decrease of propeller efficiency caused by the bubbles going into the working propeller. But, by carefully choosing the bubble injection location and thus avoiding the bubble entrainment into the propeller, the 3% power saving at a constant speed of 14kts was obtained. By taking into account the power needed to inject bubbles against hydrostatic pressure due to water depth at the injection point, this corresponds to the net power saving of 2%. Thus the net power saving by microbubbles was measured on a full- scale ship for the first time in the world.

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After the marine disaster of “Nakhodka” in 1997 at the Japan Sea, we started in 1998 a five-year research project to develop an “Optimum Towing Support System” (OTSS). OTSS is a simulation system based on the data of external forces on the sea conditions and hydrodynamic forces acting on a hull, rudder and propeller. By OTSS we are able to obtain appropriate guidelines to avoid a secondary accident and to minimize marine pollution. In the simulation, the accurate prediction of hydrodynamic forces acting particularly on a hull would be most important. Using a ten-segmented model ship, we measured the distribution of lengthwise lateral force acting on a trimmed hull in order to investigate characteristics of the hydrodynamic forces. In this paper we report the result of the investigation and propose a theoretical prediction method based on the slender body theory for the hydrodynamic forces acting on a trimmed hull.

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Fishing boats suffer from much capsizing as compared with other vessels. It may be pointed out that the stability of fishing boats tend to be poor as the bases of the severe operations and the poor management of loading condition as well as the problem with the restrictions of principal dimensions of ship. According to the recent capsizing of the trawler “Ryuho-maru V”, Ministry of Land, In-frastructure and Transport of Japan forced to check the stability of existing fishing boats and to improve the stability if not enough.
As for the improvement of the stability, the fitting of a bulge on sidewall of the vessel is one of the best solutions. This method was adopted in the old naval fleets and polar research ship “Sohya” in Japan. However, it is not commonly used. It is important to clarify for the design of the bulge what influence it has on the ship's performances not only on the stability.
In this paper, the authors have investigated into the effect of the bulge on manoeuvrability and the manoeuvring prediction, based on the model experiments and the full-scale experiments of original and enlarged fisheries research ship “Ushio-maru”. They have also investigated into the predicting method for a fishtail type high-lift rudder is proposed.
The concluding remarks are summarized as below.
(1) By fitting the bulge on sidewalls of the vessel, hydrodynamic sway damping lever is slightly reduced. In addition, the yaw damping lever is reduced by the increase of ship's mass, which keeps the almost the same stability lever of course keeping as the original ship.
(2) For the prediction of the hydrodynamic derivatives of the fishing boat with an initial trim, Kijima's formula are useful except Y'_β, N'_r, Y'_r-m'_x, using the effective draught and block coefficient of the ship. It is desirable that Y'_β, N'_r, Y'_r-m'_x are not corrected by the initial trim.
(3) For the simulation of the manoeuvring ship motion with the fishtail type high-lift rudder, the rudder open characteristic is to be altered in the proposed mathematical model. The coefficient becomes 1.4 times larger than the conventional rudder. Even for the large rudder angle such as 65°, the conventional rudder model is still available, because the actual angle of attack is decreased by the turning motion of ship.

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This paper is mainly concerned with the safe navigation between deep-drafted vessels moving each other in restricted waterways under the external force, such as wind or current. The manoeuvring simulation for model ship was conducted to find out an appropriate safe speed and distance between ships, which is required to avoid sea accident from the viewpoint of marine safety. The conditions were varied, such as velocity ratios, ship-length ratios, and separate parameters including the direction and velocity of wind and current. From the inspection of this investigation, it indicates the following result. Firstly, for the case of ship-size estimation, the lateral separation between two ships is more required for the small vessel, compared to the large vessel regardless of the effect of external force. Secondly, the lateral distance between ships are necessarily required for the velocity ratio of 1.2, compared to the cases of 0.6 and 1.5. Thirdly, in case of proximal navigation between ships under the wind and current, the low-speed vessel is potentially hazardous because the rudder force of low-speed vessel needed for steady-state course-keeping is not sufficient, compared to the high-speed vessel.

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When a FPSO (Floating Production Storage and Offloading) is required to maintain the specified position during oil producing and offloading under the external forces such as ocean current, wind or wave, exact position measurement is firstly taken into consideration. GPS (Global Positioning System) is mainly used to measure ship's position. But the position measurements using GPS contain noise. This noise has large influence on DPS (Dynamic Positioning System), therefore it is necessary to remove the noise.
In this paper, Inverse Linear Quadratic (ILQ) optimal servo theory using Kalman filter is applied to design control system of DPS. Generally, Kalman filter is to estimate the low-frequency motions of the vessel so that control can be applied to minimise the position error. But in this paper, Because we already consider motion of FPSO as low-frequency motion, Kalman filter is used to remove the measurement noise.
The numerical simulations shows the performance of the combined Kalman filter and ILQ optimal servo system.

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The simulation method of free-surface flow around hull and rudder with propeller effects on the basis of RANS equations solver has been developed. The problem of complex geometry is solved by using multi-block grid technique. Propeller effects are included in RANS equations by the body forces equivalent to mean forces acting on propeller blades calculated by UQCM on the basis of the lifting surface theory.
The present method is applied to computation of free-surface viscous flow around KCS container ship for without/with propeller condition and it is confirmed that it can accurately predict flow fields of stern region through comparison with the experimental results. Moreover, it is applied to calculate the flow around modern full ship hull and rudder without/with propeller. Consequently, its resistance and self -propulsion factors are accurately estimated. And, the difference of wake fraction due to that of propeller diameter is discussed through the analysis of the computed flow fields.

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Accurate estimation of the drag coefficient of sea-ice is very important for reliabile prediction of seaice behavior. For improving the accuracy of the drag coefficient, we have carried out a measurement of wind and turbulence on the sea of Okhotsk on board of the ice-breaking patroll ship Soya of Japan Coarst Guard.
In this study, we evaluated the influence of the superstructure and the hull of ship on the measurement of wind and turbulence by numerical simulations using a commercial CFD code Fluent (Fluent Inc.). The simulations of wind flow around the full scale ship indicated that the measuring instruments should be located at least 6m above the front-deck or at least 4m away from the bridge-house towards the upwind direction.

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Ship wave characteristics in a shallow and restricted waterway whose depth and breadth change in longitudinal direction are studied numerically.
The Euler and continuity equations are employed for the present study. Boundary fitted and moving grid system is adopted in the numerical simulation. The convection term in the governing equations and the free surface boundary condition are solved by Cubic Interpolated Pseudo particle (CIP) algorithm in order to get high resolution of wave height in far field as well as near field.
The present numerical scheme is applied to predict ship waves in shallow and restricted waterway whose depth and breadth vary in longitudinal direction.

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The present study concerns simulation of ship viscous flow at full-scale Reynolds number. The main objectives are two folds: (1) development of Reynolds-averaged Navier-Stokes equation method applicable to full-scale flow simulation; and (2) investigation on appropriate physical model for full-scale Reynolds number in conjunction with consideration of near-wall flow model including surface roughness effects. In particular, the validity and advantage of two-point wall-function approach have been investigated and the extension was made for inclusion of surface roughness effects on flow and resistance; and currently, evaluation for roughness effects on flat plate flow has been completed. The present numerical method for full-scale flow simulation is based on extension of method developed by the present author, such that, in association with standard k-ε model, two near-wall models can be employed, i.e., two-layer method and two-point wall-function method; where the latter has been shown more suitable in practical design use.

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Steady drifting condition is analyzed based on experimental and numerical data for hydrodynamic and aerodynamic forces acting on a ship in drifting motion. It is pointed out that plural steady drifting conditions have possibility to exist in wind, wave and current conditions.
Model experiments for drifting motion in regular wave were carried out. Averaged values in steady drifting motions indicate that steady drifting condition is not unique but depends on initial conditions.
Actual case of a disabled drifting ship is analyzed. Numerical calculation was carried out to obtain possible steady drifting conditions for assumed external forces corresponding to the actual case. Calculated solutions are compared with the actual steady drifting condition.

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The result of the previous validation study has shown a significant error especially for the prediction of course stability of an unstable ship. To improve the accuracy of the prediction, it will be required to estimate high accuracy hydrodynamic interaction among ship hull, propeller and rudder as well as hydrodynamic forces acting on a bare hull taking account of the detailed ship form such as stern profile and frame line.
This paper describes a study on the application of CFD (Computational Fluid Dynamics) to ship's manoeuvrability prediction at design stage. A numerical method has been applied to compute flows around a ship with a rudder in several oblique motions. Calculated interaction forces between ship hull and rudder are compared with measured ones. From this study, it is found that this hydrodynamic approach would be useful for prediction of ship manoeuvring motion

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Measurements on the effect of the Coriolis parameter on density current injected between stratified two layers were carried out. For this purpose we used a rotating tank with the diameter of 1m, which consists of tap and salt water layers. The results showed that the Coriolis force weakens the expansion of the density current and that, in the non-Rotating system, the intrusion area increases in proportion to t^4/5, where t is the elapse time, while in the Rotating system the proportion ratio is t^3/4. When the Rossby number becomes small, the patch of colored water indicating the expansion of the density current breaks up into two parts under the condition that the size of the patch exceeds a baroclinic instability limit. Also, our numerical simulation method was validated by comparing with the measuerments.

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Spilled oil sometimes causes a detrimental effect on ocean environment. Therefore, the protection and the recovery are the most important issue on the preservation of ocean environment. Dispersant is often used when the recovery is difficult. However, the use of dispersant may cause another side effect on the ocean environment. Dispersing oil by a cavitating jet seems better, because we use only pure water (sea water), and there are no side effects.
The present study shows the applicability of the cavitating jet in laboratory scale. The C-heavy oil of 10ml was spread on the water surface in a tank and was disposed to the cavitating jet from 45 degree below. The dispersed oil was sampled and measured by a microscope. The diameter of the dispersed oil was less than 50 micrometers and the concentration was 0.2-1.4 percent. This result shows that the cavitating jet is a promising tool in spilled oil treatment.

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The ballast water contains many planktons, fish eggs, etc. which sometimes gives a detrimental effect on the environment where thousands miles away from the ballast water is loaded. The present experimental study showed that the high-speed water flow could destroy planktons. The generation of cavitation should increase the effect of destruction.
We examined two methods; those were two nozzles in a pipe, and cavitating jet flow into a chamber. Both were promising and should continue the experiment to find the best set-up to destroy planktons.

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Suppression of the swinging load is very important for increasing the operability of a floating crane in waves. In the first report, we proposed a effective method of suppressing a swinging load through controlling the floating body motion itself adding pnumatic actuator system. This was a very unique idea and the effectiveness of this method was confirmed through model experiments and numerical simulations, especially in long crested irregular waves. In the second report, we report about the results of this confirmation in more realistic experimental condition and by using more advanced controlling system also in directional spectrum waves. Namely, the swinging load is moved up and down direction in directional spectrum waves. This case, the natural frequency of swinging load is changed according time passed and transverse swing occurs. Furthermore, optimal control was introduced in numerical simulation.

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When precise GPS positioning is applied in ocean, the baseline length becomes too long, since the reference point can't be placed near. In the present report, a solution for the problem is proposed from a new viewpoint. According to the present method, a possibility for the precise GPS positioning may be developed. In the present report, determination of initial phase ambiguities not influenced by the baseline length is discussed.

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Bayesian modeling procedure is applied to online analysis to estimate directional wave spectra based on ship motion data. The proposed method can deal with the nonstationarity of ship responses that comes from the ship maneuvers such as changes of the course and speed. In order to cope with the nonstationarity included in the time history data, instantaneous cross spectrum analysis based on T-VVAR (Time Varying Coefficient Vector Auto Regressive) modeling procedure is introduced. Moreover, Bayesian modeling procedure is transformed into an online algorithm. Some numerical experiments were carried out to examine the proposed method. Using an array of wave probes, measurements of time varying directional wave spectra were simulated. It is shown that the estimated directional wave spectra agree well with the incident wave spectrum and the proposed method can cope with the nonstationarity.

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An on board system for wave data analysis and application to ship operation has been developed. The system consists of wave probes, accelerometers, a soft-ware of analysis and a wave data display tool. The former two are used to estimate the encountering wave surface elevations on ship hull. The main parameters of waves, i.e. the wave direction, the mean wave period or wave length and the significant wave height are calculated by using the encounter wave elevation data at three positions on ship side.
The obtained wave parameters are used to show the situation of own ship at sea on the figures of operational guidance, so that the master can judge how to change the ship course or speed for preventing dangerous situations.
This paper presents a simple method of wave analysis using cross spectra of wave data at three positions on ship sides and the examination of the method by numerical simulations and model experiments in directional waves. The test results on actual vessel at sea will be presented.

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A series of model tests in waves were conducted to measure the green water loads that act on deck due to deck wetness using the model of general cargo ship. The ship, which is finer than bulk carriers, is the medium sized freight container carrier (L_pp: 160m, C_B: 0.663). For the examinations of effects of the ship's forward speed on the green water loads, the model tests were made in ship speed conditions of 2 knots and 4 knots. The tests in regular and irregular waves were done in head seas. As to the tests in irregular waves, the significant wave height (H_1/3) is 12 meters and the mean wave period (T₀₁) is 10.4 seconds.
In order to assess the experimental results quantitatively, maximum value and probability density function of green water loads were estimated by the use of estimation methods that were developed by the one of authors. Having compared with measured data, it was found that its estimations were in good agreement with measured data. It is concluded that the experimental results were rational.
Experimental results for general cargo ship were compared with the results for bulk carrier. Although the test conditions, such as the significant wave height, the mean wave period and the ship speed, of the two model tests conducted were different (Bulk carrier H_1/3=10.6m, T₀₁=14.0 sec., ship speed=1.4kt, General cargo ship: H_1/3=12m, T₀₁=10.4 sec., ship speed=2kt) and severer for the general cargo ship, it is found that the green water load on the deck of the general cargo ship are smaller than those of the bulk carrier. It is concluded that green water load in the regulation should be different for different ship types

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Model tests were carried out in order to develop a practical estimation method of impact pressure on the bow flare. Model of a large container carrier was used. Impact pressure on bow flare, ship motion and so forth were measured in various wave height and period. It is found that impact pressures have relation to ship motion and wave height has much effect on impact pressure.
Relative water height and vertical acceleration, which is key factor to estimate relative speed and angle between ship and wave accurately, were estimated by taking into account of nonlinear effect of ship hull. Having compared with measured data, it was verified that its estimations were in good agreement with measured data in various wave height conditions.
Based on these results, practical prediction method of probability density function of impact pressure on the bow flare was proposed. Probability density function of impact pressure is derived by the combination of Chuang's method, which is the estimation method of impact pressure by the use of relative speed and angle between ship and wave, and probability density function of relative water height, which is estimated by taking into account of nonlinear effect of ship hull. Having compared with measured data, it was confirmed that this method gives a good estimation for the probability density function of impact pressure on the bow flare.

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Recent model experiments by the authors indicated that bow-diving is one of the crucial capsizing modes for a ship traveling in following and quartering seas with high forward velocity, while only a few research attempts on this phenomenon were reported so far. In this paper, basic features of bow-diving are discussed with measured time series. As a result, it is concluded that bow-diving is associated with surf riding and triggered with submergence of bow bulwark top. Then, by statically calculating vertical distance of bulwark top from wave surface with Froude-Krylov assumption, the possibility of bow-diving observed in the experiment is reasonably well explained.

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The hydrodynamic interaction between a submerged non-lifting body and lifting bodies, i.e., hydrofoils, is studied. So far it has been confirmed that the hydrofoil producing the downward lifting force reduces the wave resistance drasticly due to the hydrodynamic interaction with the non-lifting body. This paper investigates the hydrodynamic interaction effect on the unsteady hydrodynamic forces, the added wave resistance and the wave field through model test and numerical computation by Rankine panel method. Numerical results and experimental results are compared and the hydrodynamic interaction effect is discussed. We have found good agreement between numerical and experimental results and it has been confirmed that the interaction effect is not so significant in the present case.

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In order to improve the stability and to increase the working area for fishing vessel, bulges are often added on ship sides from underwater part up to upper deck. From the view point of seakeeping quality, it is important to clarify the effect of bulges on ship dynamic response as well as static stability. A fisheries research vessel“Ushio-maru”has been rebuilt (elongated and bulges fitted) recently. In this paper, we present the results of investigation into its stability improvement and study on the influence of bulge on its motion in waves by model experiments and theoretical calculations. It was shown that stability improvement is considerably achieved by fitting bulges. In addition, resonant roll motion was slightly reduced due to damping effect of bulges. It was also found that there are no significant difference in heave and pitch due to the existence of bulge. On the other hand, roll motion in beam and quartering long waves increase. Furthermore, at-sea seakeeping tests of the ship with bulges were conducted and then motion characteristics in real ocean waves is described. Finally, authors point out the merits and demerits of fitting bulge to fishing vessel.

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There are some studies on reduction of hyclroelaastic deflection of a very large floating structure. However, the wave drifting force increases when the deflection is reduced. It is very difficult to reduce the deflection and the wave drifting force at the same time.
This paper proposes an aircushion-supported type for a very large floating structure. This type may be able to reduce the deflection and the wave drifting force simultaneously. Therefore, we show the theoretical analysis method for the hydrodynamic force of the aircushion-supported flexible floating structure. This analysis method is based on the pressure distribution method. The free water surface condition in the aircushion is satisfied when the boundary problem is solved in this method.
In this paper, the deflection characteristic and the water elevation in the aircushion and around the structure are shown. We discuss them. Moreover., the calculation results by the pressure distribution method and the three-dimensional analysis based on the singular point distribution method are compared in order to prove validity of the program code and the corresponding theory.

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The purposes of the study are to investigate non-linear features in large amplitudes of ship motions experimentally and to clarify the mechanism of these features. In the first report, a new non-linear feature of ship motions in high waves was presented. In heavy beam seas, large amplitude rolling motion occurs not only in frequency region of the roll resonance but also in wide frequency region higher than the resonant frequency, and a kind of jump phenomena of rolling motion appears. The cause of these phenomena is that drift motion induced by high waves changes encounter frequency and shifts roll resonance to higher frequency. Roll natural period of the model ship used in the experiments are close to heave natural period. There is quite a possibility that a roll natural frequency influences on the non-linear features in the rolling motion in heavy beam seas.
In this paper, additional experiments are carried out to investigate relation between roll natural frequency and roll-resonance-shifting to higher frequency, and to confirm a kind of jump phenomena of rolling motion. The experiments show that roll-resonance-shifting to higher frequency is significant with increasing roll natural frequency. This phenomenon is induced by increasing drifting velocity due to increasing roll natural frequency. A non-linear feature of heaving motion is also confirmed near heave natural frequency.
In the experiment, the model ship is knocked to induce jump phenomena during the measurement of ship motions in heavy beam seas. The results show that two modes of ship motions appear with different encounter frequencies for the same regular wave.
To reveal the reason of the non-linear features shown in the experiments, non-linear hydrodynamic characteristics in the motion equations for drifting and roll-heave-sway coupling motion are investigated.

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As a part of the project study concerning on ship structural design for oil spill prevention by collision, optimal design of flexible bulbous bow structure is studied to absorb kinetic energy of the colliding ship. Such a flexible bulbous bow is named as buffer bow. To formulate design criteria of the buffer bow, the hydrodynamic impact forces acts on the bulbous bow was studied theoretically and experimentally. For theoretical study, shape of the bulbous bow was approximated by an ellipsoid and von Kárman's momentum theory was applied to estimate the slamming impact loads with given impact velocity of the emerged bow to free surface. Wagner's impact theory was also applied to study the effect of free surface swell up. Based on the momentum theoy, an estimation method of the impact loads was proposed. To validate the estimation method, a experiment was conducted at the 80m square tank of NMRI. A self-propelling container ship model was used for the experiment. The vertical and lateral shearing forces and bending moments at the root of the bulbous bow were measured. In this paper, the results of the study are presented.

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In the proximity of the water surface, aerodynamic wings show considerable high lift/drag ratio. This effect is the basis of Wing-In-Surface-Effect-Ship(WISES ) which supports its hull in a very low altitude from the water surface by a system of aerodynamic wings. Wind tunnel investigations of the wing-in-surface-effect require simulation of the water plane condition and a number of test cases ranging in both angle of attack and altitude. These are no easy tasks.
In recent years, computational fluid dynamics of three-dimensional flow around complex geometries became popular. This enables us to examine the flow around complex configurations of WISES on a mid-range computer and this compensates for the difficulty of experiments.
In this paper, aerodynamic characteristics of three-dimensional wings in the surface effect are investigated by a commercial CFD application. Tested configurations are two wing sections of Clark-Y and S-shaped wing with and without endplates. All wings have an aspect ratio of 1. Numerical results and visualization of the flow field show the effectiveness of endplates and the S-shaped wing section in three-dimensional wings in the surface effect.

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A huge amount of data has been produced from computations and experiments in Computational Fluid Dynamics and Experimental Fluid Dynamics. Owing to the volume of data, it is quite difficult to extract useful information from these data even if using flow visualization. In this paper, we propose a framework of analysis support system for visualized information. First, a simplification of visualized information for the purpose of an efficient information extraction to analyze a flow field is discussed. It is shown that critical points on a velocity field and a vortical structure obtained by substituting the vorticity distribution into discrete vortex elements become a starting point of simplification. And then, we demonstrate that several techniques of map generalization are valid to simplify the visualized information, and the results simplified by the generalization can be effectively visualized using nonlinear magnification. Second, we consider an annotation system. Annotations are added to the clustered or symbolized objects extracted from the simplified information. Finally, we show a framework of the system, and several examples are demonstrated. It will be considered that our proposed system is useful to analyze the visualized information.

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The environmental impacts of an imaginary very large floating structure on marine environment, especially on carbon circulation around the structure, are examined using numerical simulation by means of coastal ecosystem model. After validation of coastal ecosystem model by comparing predicted results with observed ones, the impacts of the floating structure moored off Oppama or off Haneda are discussed. As a result of several computations, it is revealed that growth rate of sessile organisms adhering to the floating structure are smaller in the sea area off Haneda, where current velocity of sea water is slow, because particulate organic matter and oxygen are not supplied sufficiently. On the other hand, in the sea area off Oppama, seawater flows southward constantly at the speed of about 0.1m/s, and organic matter and oxygen are supplied appropriately, so sessile organisms can sustain their biomass. The biomass of sessile organisms per unit area of the floating structure moored off Oppama is much larger than that in the general tidal flat estuary. Further, the impacts of activities of sessile organisms on carbon circulation in Tokyo Bay are examined. Then it can be said that sessile organisms retain organic matters in the bay, which may otherwise flow out from the bay to the outer sea.

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Wave drift forces play an important role when a vessel is floating in the vicinity of another vessel or, floating structure. The numerical accuracy in the computation of the wave exciting forces and the hydrodynamic forces of multiple floating bodies influences the motion response that eventually affects the second order wave drift forces of each floating body. The present study is based on the far-field method where the velocity potential is calculated by 3D sink-source technique. In order to justify the validity of the present calculations, some comparisons are made for simple multi-body floating systems like multiple floating cylinders and cylindrical body with box shaped body. The numerical calculations have been investigated for a parallel arrangement of FPSO and an LNG carrier. The computations of motion responses and drift forces are carried out for a number of different wave heading angles and for different separation distances between the FPSO and LNG carrier. The numerical results are compared with the experimental ones as well as with previous computations to illustrate the improved numerical accuracy of the present computations. It has been observed that due to the lack of accuracy in the numerical scheme adopted for the computer code, the computed results of drift forces sometimes shows completely opposite trend than that of the experimental ones.

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A Very Large Floating Structure (VLFS) is expected as a new utilization of the ocean space. Rigidity of VLFS is, however, relatively small, so that an hydroelastic response of VLFS in waves should be considered. Many researchers studied on the elastic response of a pontoon type VLFS, in addition, on that of column support type VLFS. The VLFS supported by columns shows the smaller elastic response than that of the pontoon type VLFS. In the 1st report of this paper, we have discussed about hydrodynamic responses of a column with footing which has a wave-free frequency on wave exciting force and also examined the hydroelastic responses of a VLFS supported by a large number of the columns in regular waves.
In this paper, we investigate on the charcteristics of hydroelastic behaviors of a VLFS supported by a large number of footing-columns which have two wave-free frequencies. And then, we disccuse about the hydroelastic behaviors of a VLFS in irregular seas based on spectral analyses. Furthermore we compare the hydroelastic responses of VLFSs among supported by columns without wave-free frequency, supported by columns with one wave-free frequency and supported by columns with two wave-free frequencies. In the analyses, the hydrodynamic forces of the single column are calculated by using 3-dimensional source sink method, and the hydrodynamic characteristics of VLFS are obtained by using hydro interaction theory.

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In recent years, there are a lot of researches on hydroelastic responses of a Very Large Floating Structure (VLFS) which has several kilometers both in length and width. In the most of these researches, a geometric shape of the model is pontoon-type rectangle VLFS and it assumes that the sea depth is constant. But if we have a plan to construct such large structure in actual coastal area, it is quite difficult to find a vast flat bottom of the sea in Japan. So, in this paper we propose a prediction method on a hydroelastic behavior of VLFS extending the eigen functions expansion method to that including the sea bottom topographical effects. In the analyses the hydroelstic effect of the VLFS is also analyticaly taken into account. One of the improve points of the present method is that the problem of any supportive type of VLFS (i.e. pontoon supportive, column-supportive etc.) can be analyzed by this method. In other words, we can treat the pontoon type problem as a box-like shape column supportive type.
Finally, some numerical results are carried out and discussions on the validity of the present method and the effects of seabed topography are made in this paper.

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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 and moment on VLFS. Parametric study is done to have wave drifting moment characteristics with respect to size of VLFS and incident wave angle. Also done is mooring response analysis for 5, 000m-long VLFS, where wave drifting moment is found to play a minor role in contrast with steady wave drifting force.

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The objective of present paper is to develop the practical numerical analysis system for calculating responses of motion and mooring force on floating structures induced by tsunami in shallow sea region.
In the present analysis system, incident wave profile of tsunami in shallow sea have been assumed to dispersed wave based on the data base of tsunami height in all over Japan. And more boundary value problem for dispersed wave have been analyzed by the boundary element method in time domain and also the responses of motion and mooring forces for floating structures have been calculated by convolution integral method.
The numerical calculation by the present method have been carried out and the results by present method have been compared with the results by CADMASU-SURF based on NS equation and with the experiment results. From these comparisons, the authors have discussed as follows: 1) From above comparisons, the accuracy and the usefulness of present numerical method have been examined. 2) From the comparisons between the numerical results for dispersed wave and solitary wave, the deference for characteristics of motion and mooring force have been discussed

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The objective of present paper is to examine the characteristics of sea-shock responses of floating structures by using practical method (so call impedance method) considering the effect of seabed. In the present paper, the impedance method, which was considered the reflection characteristics of earthquake wave by using impedance ratio, was formulated and the characteristics of hydrodynamic forces by present method was compared with the results by the method of elastic sea ground and wave tank experiments and evaluation method of optimum impedance ratio was discussed.
Furthermore, the characteristics for sea-shock response of floating structure were calculated by the impedance method with optimum impedance ratio and also these numerical results were discussed.

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The dynamic hydro-elastic responses of floating structures to solitary waves are investigated and discussed in detail through experiments and numerical simulations. The fission phenomenon of a solitary wave is discovered when the wave propagates under a flexible structure. Different from the soliton fission occurring on a free water surface, the phenomenon is induced by the difference of the propagation velocities of the elastic deformation of structure and the wave pressure acting on the bottom of the structure. The fissioned waves are defined as three patterns of a leading wave, a transiting wave and a trailing wave. Which pattern a solitary wave will be fissioned in depends on wave conditions, especially a water depth, and the structural properties, such as its bending rigidity.

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Two methods for computational reconstruction of fluctuating flows in the ocean based on field measurements are suggested. Here full-3D CFD treatment with the spatial scale of O(100m) - O(1000m) is taken into account. In the first method, the fluctuating flow based on measurement data is generated at the inflow boundary and introduced into the computational domain. In the second method, small wavenumber components of fluctuation in the ocean are forced in the computational domain, and large wavenumber components are evolved freely in the computation. The results of each method are discussed with comparing with the measurements, and their availability is suggested.

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In the present study, some attempts have been made to investigate the effect of corrosion pits on the strength of hold frames of bulk carriers. Firstly, shapes of corrosion pits observed on the hold frames have been investigated in detail. It was shown that the shape of the corrosion pits is a circular cone and the ratio of the diameter to the depth is about S to 1. Secondly, a series of tensile tests has been conducted and it was pointed out that when there is pitting corrosion, the tensile strength decreases gradually and the total elongation decreases drastically as the thickness loss increases. Thirdly, a compression test has been performed and FE-Analysis has been carried out to simulate the experiment. The buckling behavior can be well simulated by elasto-plastic analysis when taking into account the shape and the position of the corrosion pits.

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A series of buckling eigen-value calculations and elastoplastic large deflection analyses of simply upported continuous plate with cutout under thrust has been performed. Firstly, simple formulae for estimation of elastic buckling strength have been derived based on the results of eigen-value calculations. Secondary, it has been clarified that the buckling strength evaluated by the existing plastic correction methods exceeds the ultimate strength in some combinations of plate thickness and cutout diameter. So, new plastic correction formula considering the yielding effect for estimation of buckling strength of continuous plate with cutout has been proposed. Finally, by focusing on the characteristics of ultimate strength obtained by elastoplastic large deflection analyses, simple formulae for estimation of ultimate strength of continuous plate with cutout have been derived.

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Domestic shipping companies should decide whether a new or existing line is profitable or not. We propose a method to find profitability for an examining sea line and proper specifications of a ship for it. The method is made of PC programs including an estimating method of cargo demand and calculate a fleet condition, ship specifications and shipping account for a long haul ferry or RORO ship line.

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This paper presents a design support system for basic design of ships. The system aims at supporting designers by presenting documents needed for each task according to design processes. In order to construct our system, several approaches were adopted. At first, an analysis of basic design process using UML was made. Authors understood its workflow and extracted a data list to make documents for each step of the workflow. Secondly, Semantic Web architecture was introduced to structuralise ship design documents. By applying Semantic Web technology, users can query to collections of documents as if using relational databases. Authors implemented the system and evaluated it through an example of basic design. The system shows its efficiency in the evaluation.

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For storage and transport of liquefied gas such as LNG or LH2 (liquefied hydrogen), it is of great importance to reduce the boil off gas to a minimum. The thermal insulation system is playing a significant roll here. Though the specification of tank insulation should be decided by the boil off figure of a desired total system from a view point of an economical and practical use of it, the reduction of evaporated quantity is being demanded stronger, and any achievements to enhance the reduction are appreciated. The authors have introduced a new concept for enhancement of insulation efficiency by indirectly using the cold boil off gas as a protective shield or a heat sink to limit transmission of heat to the tank/cargo. To verify this theory of “vapor insulation system”, an experiment based on cold gas flow was carried out in a small scale apparatus to analyze carefully the effect on the heat transmission with and without cold vapor flow. These results were implemented in a calculation model of a spherical tank for LNG and LH2, and combined with some parameters such as gas flow quantity, gas temperature and location of gas passage. Based on this work realistic examples of design were proposed for a new insulation system. The configuration takes into account the concept of the small leak protection system for MOSS spherical tank. The principle of this new insulation concept proposed is that cold nitrogen gas which is produced by heat-exchange with the boil off LNG or LH2 vapor flows through a small passage created in the insulation structure. The upward flow of cold gas through the annular space around the tank will absorb the heat from the hold space of the cargo tank before it reaches the valuable liquid cargo, and it will simultaneously work as a leak detection system of cargo.

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In recent years lithium has been used increasingly as a second battery, particularly in the field of electric information device, because of its high energy density and output voltage. However, we import the necessary amount of lithium from foreign countries since there is no available lithium mine in Japan. In order to secure constantly a sufficient amount of lithium in Japan, special attention has been paid to lithium ion dissolved in Seawater. A recent estimation indicated that at least 200 billion tons of the lithium ion are dissolved in the whole seawater. We propose a floating system to extract lithium from seawater using such ocean energies as sea wave and sea current. For three years from 2000 to 2002, we performed several investigations to develop techniques for practical use of the floating system. In this paper, we report the results of our investigations, as the first step toward the practical use.

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On underwater robot manipulators, high speed and high precision are basic requirements in order to improve efficiency of operations. To satisfy these requirements, feedforward control inputs are crucial. For making feedforward inputs, one of the methods is to estimate all parameters of underwater robot dynamics. However, parameter estimation of hydrodynamic coefficients is very difficult because the dynamics is complicated. To overcome such a difficulty, we apply iterative learning control to underwater robots. In this paper, we theoretically discuss the performance of iterative learning control for underwater robot manipulators. Moreover, the effectiveness of the learning control is experimentally verified through several experimental results.

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Extensive inspection of underwater structures can be very hazardous and requires a very high degree of automation in the use of AUVs (Autonomous Underwater Vehicles). In order to accomplish the autonomous inspection task, AUVs should identify and investigate an inspection target by means of image processing.
In this paper, an image recognition method is proposed for AUVs to identify an inspection target that may have been deformed by marine bio-fouling or corrosion. The proposed method incorporates improvement of the lighting method that also makes full use of underwater environment's characteristics for identification of a deformed object. This method allows robust recognition of a deformed object with small computing power available on AUVs. As an example, a recognition method for sacrificial anodes, an important inspection target, is addressed. The effectiveness of the proposed method is demonstrated by simulations and also by field experiments carried out under the bottom of Mega-Float; a very large floating artificial land located off Yokosuka.

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Many fire accidents in engine rooms of ships and marine structures come into existence in the world, and the unexpected burning of hydrocarbon liquid, such as fuel oil and lubrication oil, tends to be a good half of those primary cause. For the preventive design of oil burning fire in engine rooms, it is necessary to be grasped entirely the oil pool fires phenomena by an analysis taking thoroughly account of the governing factors and the characteristics of flammability liquid fire
In order to investigate the distinctive factors of fire spread and extinguishing by some numerical simulations of fire accident in an engine room, the basic experiments on oil burning are executed in the condition of (1)oxygen rich atmosphere, and (2)oxygen lean atmosphere. Furthermore, the oil burning phenomena in enclosed-compartment is estimated qualitatively using a simplified mathematical model with a principle feature of enclosure fire. From the results of these experiments, it can be clarified as for threshold conditions of fire spreading, thermal properties and states of oil pool fires.

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Approximately 500 mega-tons as much as 25% of input resource are disposed a year as refuse. And the municipal refuse that is approximately 50 mega-tons, and more significantly 70% of the municipal refuse are disposed by incineration plant of all municipalities districts of Japan.
In 1983, the inhabitants near the location of incineration plant were thrown into a panic on realizing the high density dioxin emission from the flying ash of the refuse incineration plant, and this trouble has developed into a social problem in Japan. So approximately 4600 plant of the refuse incineration as much as 17% are suspended to operate because of the dioxin emission control by the Japanese Government.
It is low possibility to operate the refuse incineration plant again, because of the financial difficulties of municipalities and the difficulties of a general consensus among inhabitants in the neighboring areas of plant.
In this paper, a concept of the refuse management system that is the combination system of the floating refuse incineration plant and the refuse collection systems on shipping are proposed for solving these defective points, as the practical example of applying the proposal concept to the region of Ariake sea and its feasibility study are stated briefly.

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The processes of the engineering design are generally held on from abstract objects to specific objects gradually. This stepwise process holds true with the design of merchant ships. And the product information is describes in two ways; one is the extensional way, the other is the intentional way. The concept of extensional description is practiced as configuration design and layout design. The concept of intentional description is practiced as parametric design.
On the other hand, authors already propose the top-down oriented design approach. In this approach, two concepts are proposed as an elementary factor of design information model;“information of entity”and“information of attribute”. Furthermore two information flows are proposed:“specification for model structure”and“specification for model status”. The specification for model structure means a structure of product model described by information models of entity and attribute. And a specification for model status means definitely description of information of relation and attribute values in the defined model and management that information. The extensional description of product model information is corresponded to specification for model structure, and the intentional description is corresponded to specification for model status". Thus top-down oriented design approach is applied to merchant ship design. The prototype system based on this concept is implemented, and some examples are shown.

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River systems are expected to have a great potential to transport cargoes especially under disaster conditions. In Hanshin Earthquake disaster occurred in 1995, ship transport of relief goods by rivers worked effectively. Furthermore the alternative routes other than transportation on land under disaster circumstances are required strongly. The ship transport of relief goods by rivers meets with this requirement.
This paper describes a way to estimate the capacity of ship transportation by rivers with multi-agent simulation. Simulation results clarify the structure of bottlenecks that restrict the amount of transportation under disaster circumstances described in this paper. Firstly the supplying capacity, such as loading speed to vessels, is most important factor. Secondary the receiving capacity at a birth of suffering areas becomes important. If the capacity of both receiving and supplying is sufficient, the number of ships results in shortness.

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