From the viewpoint of an environmental conservation, it is often required to eliminate air bubbles in cooling seawater discharged from process plants to sea area. The air bubbles are generated due to a nappe from a weir. A de-aeration chamber is one of technology to eliminate the air bubbles. For the design, a volume and size distribution of air bubbles in seawater are essential engineering information, however, few quantitative investigations are carried out. Therefore, the volume and size distribution of air bubbles generated due to the nappe were measured for seawater and tap water, and it was found that the size of air bubbles in seawater became smaller than that in tap water, etc.

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In the previous paper, model tests have clarified that real stern end immersion Ir plays an important role for the stern wave resistance due to a transom stern at the lower ship speed range. Details of Ir's role for the stern wave resistance have, however, not been clear. In this paper, a method to estimate the effect of Ir is developed at first. Then above described model test results are analyzed by the method to clarify the details. As a result, not only the effect of Ir on the swbf but also acceleration itself at the stern end due to decrease of Ir are found to be important for the stern wave resistance due to the transom stern at the lower ship speed range of FrI <3.1.

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This paper describes the effect of compressibility of fluid outside the vibrating ship hulls on the inertia and damping forces as the fluid-structure interaction. In this investigation 3-D finite element analysis is carried out to calculate the pressure fields around the uniform beam vibrating vertically with sinusoidal natural modes. Added mass and damping coefficients can be expressed as functions of frequency and nodal distances. It is found that the added mass coefficient may increase up to 5 % for the hull girder vibration of typical VLCC and bulk carriers if the compressibility is considered.

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Sharper bow waterline shape can reduce the wave added resistance at sea more than that for conventional blunt bow. Ax-Bow is an example based on such principle. The bow with sharp waterline at all waterline heights can reduce the resistance further, but the effect of the bulbous-bow is expected to become deteriorated. According to the model test results on a low speed full ship, such bow shape with all sharpen waterlines show the same performance in still water, and better performance in waves in comparison with a conventional blunt bow.

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The authors have proposed a 20 feet container size Packaged electric Generator Unit (called PGU herinafter),which is integrated with a 800kw electric generator coupled with a 900 rpm diesel engine. The newly introduced marine machinery plant consist of many PGUs that cover both power sources of ship propulsion and onboard electric services. Thus, this new plant aims at higher reliability of ship's propulsion system having the redundancy by providing apare PGUs on one hand, and un-manned ebgine room by maintenance-free onboard on the other. This papaer introduces the above concept, which adopts coastal cruise ship as model ship.

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[in Japanese]

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Wind force acting on a ship is reduced by square corner-cut on a accommodation structure and/or a ship hull. The effect of these methods is confirmed by wind tunnel tests. The test result for its application to the accommodation structure shows the wind resistance reduction by the ratio of about 10%. The square corner-cut on the hull structure of PCC gives the side wind force reduction by about 20% according to the wind tunnel test results. The effect of these reduction to the reduction of speed loss or drifting of ships is predicted.

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In recent years, some ocean yacht races had experienced disasters in which several entries suffered capsizing and results in the loss of lives. From this reality, it is pointed out now that there is a possibility of overlooking of survivability of latest sailing yachts.
The aim of this research is to ascertain whether such drawback is common to the latest yacht design or not. For this purpose, the authors attempt to develop a database of principal dimensions of yacht hulls, sails and rigging since 1940s. The total number of yachts used here is more than 500.
This database clearly indicates an obvious tendency in transition of yacht design from safer to faster.

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Present authors propose a new type of WISES with canard configuration and forward mounted propellers.
In this concept, the ship can simply takes bow-up position to receive high lift force with large attack angle. Besides that, the high-speed wake from forward mounted propellers prevents the canard and the main wing from stall, even in a high lift condition. This type of WISES is expected to have good performance in rough sea states.
For the primary demonstration of the concept, authors built a radio controlled self-propulsion model.
In the paper, the concept of the canard type WISES, the remotely operated model and some results of field tests are described.

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For the marine developments, numerical simulations of the tidal current became very important.The tidal current is influenced by the bay shape, the depth wind, river flow, air temperature, and etc. but systematic parameter studies are not made so much. In this paper, to confirm the applicability of the simulation by multi level model,1)simulations of the supposed rectangular bay and comparisons with the linear theory, and 2) simulations of the Ariake sea and comparisons with the experimental data are made, considering the effects of wind and river flow.As another application, from viewpoint of ocean nourishment,3) sediment transport from the sea bottom layer.

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In order to predict the minimum requirement of thickness of MR construction for ship hull from the view point of avoiding the buckling mode of whole plate, which will lead the whole hull to a crucial damage, the authors studied the unidirectional glass fiber reinforced epoxy laminar as a case study on the buckling mode transition from the global one to micro fiber with increase of thickness and volume fraction. We calculated the compressive strength using an elastic plate buckling equation and an equation for micro buckling of fiber. The calculation result was verified by an experimental data. The whole tendency through the considering thickness and volume fraction showed good accordance.

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The new marine paint made by chitosan and its derivatives is developed. The effect of hydrogel structure of chitosan to the frictional resistance is investigated usingrotating cylinder type shear stress meter. The resistance test in the towing tank is also carried out using high speed PWC model ship. The drag reduction due to hydrogel structure is promissing.

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In the present study, a methodology for feasibility study of a large conventional car ferry operating in long distance route is developed. In the method, firstly, shares of a large conventional car ferry as well as other transportation systems are determined based on a Benefit-Cost-Risk model. The model is built up with including factors of total fare, required time to travel, comfort, convenience, exhaustion, safety, and motion sickness.

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