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The world's first Liquefied Hydrogen (LH2) Carrier which will transport LH2 from Australia to Japan has been built. At Japanese port, reducing the tank pressure will be required for the safe tank operation. However, pressure reduction will cause flashing, leading to an excess of the venting capacity or liquid leakage. Hence, the purpose of this research is to clarify the pressure reduction rate and liquid behavior through experimental and numerical approaches respectively. Pressure reduction experiment under high liquid level condition was conducted by using 30 m3 tank filled with saturated LH2. The experiment showed that the pressure recovery occurred at the beginning of depressurization, and then the pressure decreased based on the equilibrium state. From numerical analysis by VOF based in-house CFD code, it was found that the pressure recovery was caused by the boiling delay, and the tank pressure followed the saturation pressure after the liquid fully stirred.

SEA-Arrow (sharp entrance angle bow like an arrow) has no protrusion of the bulbous bow to reduce bow waves and has a transverse stiffening system in the narrow bow space to apply the buffer bow concept. This system has lower longitudinal stiffness than a conventional longitudinal stiffening system and therefore has buffer characteristic in ship-to-ship collision. A comparative collision study of SEA-Arrow and the conventional bulbous bow was conducted using elasto-plastic finite element analysis. A collision scenario where the striking ship hits the side shell of tanker midship perpendicularly was selected. The results showed that the buffer bow characteristic of SEA-Arrow is superior to that of the conventional bulbous bow, since much more energy is dissipated by the plastic deformation of striking and struck ships until the inner shell of struck ship ruptures.

A pro-active safety management system for ship structures that quantifies the aging effect such as by fatigue and corrosion on the ship's structural integrity is proposed as a new approach to the ship's structural surveys that have conventionally been made according to a more passive management system. Some of the authors have developed a compact fatigue damage sensor that can detect accumulated fatigue damage in welded structures by attachment to the member and inspection after a certain period. The authors have applied this sensor to the hull structures of an LNG carrier for experimental purposes, ascertained its long-term durability under the severe environment to which the ship was exposed and obtained quantitative data on the accumulated fatigue damage. In this paper, the authors propose a fatigue management system using this sensor called the Hull Aging Management System and propose it as a pro-active safety management system for LNG carrier hull structural aging and introduce a method to i...

There is a growing tendency to require increased service, beyond the design life, for steel structures such as bridges, vehicles, railways, vessels and construction machinery etc. by the implementation of regular maintenance procedures. During this maintenance products are inspected at relatively short intervals and, based upon the results of inspection and diagnosis, repair and reinforcement work is carried out as the need arises in order to prolong the lifespan. In addition to visual observation, the acoustic tapping method, magnetic powder flaw detection, penetration inspection, ultrasonic flaw detection and the latest measurement apparatus are employed for inspection; however, these conventional flaw detecting methods aim to detect unfavourable conditions, such as defects, cracks, corrosion, deformation, abrasion etc., which are already present within the structure, and are incapable of detecting latent defects and barely valid for fatigue cracks which are likely to occur in the future. Furth...

Experiments were performed to observe the flow patterns and the behavior of a two-phase (liquid/gas) flow in a spiral tube under microgravity. The liquids used were ethyl alcohol and R113. The microgravity environment was performed using a 10-m-class drop tower, which can maintain a gravity level of 10 −2 g for about 1 s. Photographs of the flow behavior were taken by a micro CCD camera and transmitted to a video cassette recorder. Preliminary models to explain the observed flow pattern map are evolved.

In order to predict various phenomena related to flow and heat transfer in space, it is necessary to carry out experiments under microgravity. In this paper, we describe the behavior of a horizontal two-phase flow under microgravity utilizing a drop tower 6.1m in height, which realizes microgravity conditions of less than 0.02G(G=g/g0) for about one second when the capsule is falling down. The experiment was carried out in a horizontal transparent acrylic resin tube of 10mm I. D. and 250mm length, using Freon-22 and water as the working fluid, in a superficial gas velocity range of 0.021m/s to 5.05m/s (ReG=58∼1.4×104) and a superficial water velocity of 0.022m/s to 0.456m/s (ReL=246∼5.1×103). The flow patterns obtained under microgravity were compared with other data under actual microgravity utilizing a drop tower. Furthermore, the base liquid film thickness, the height of waves and the period of waves in the region of annular flow, were obtained from a measured shape of waves. Then, the relationship between these values, gas Reynolds number and liquid film Reynolds number was obtained. Also, the void fraction under microgravity could be expressed using the distribution parameter and the Martinelli parameter.

A concept of modularized inflatable space structure, which is composed of inflatable elements supported by a truss structure for high-precision reflector missions in relatively near future, is proposed to avoid some difficulties of conventional inflatable concept, such as the lack of inside hard points, and the precisely accurate manufacturing process. Some fundamental characteristics for surface accuracy of inflatable elements are studied, appropriate truss back-up structure is investigated, and the relevant prelimimary test results are described. Some aspects of the application of the concept to space VLBI antenna are also introduced.