A method of successive approximation to obtain an axial symmetric cavity flow between two solid disc or some head and tail is proposed and computational examples are shown. In this method, at first the integral equation to determine velocity deviation by small deformation of a body or free stream surface is introduced by variation calculus. Then making use of this equation, deformation of a body or stream surface to give a prescribed velocity distribution is determined. Computational examples show its accuracy and rapid convergence.

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Investigation on the damaged stability might come into a territory of ship calculation, but not so many papers appear in the past. This problem was newly discussed and legislated at SOLAS Convention 1948, while the rules for subdivision i.e. longitudinal damaged stability, had been in force since 1927, taking the opportunity of the S.S. Titanic's catastrophe. In consequence, considerable difference and unbalance can be seen between the both stipulations in SOLAS rule, in respects of thinking way, description, interpretation and application of rule itself. In this paper, a few examples of investigations on the damaged stability are introduced in an "Omni bus" style, as follows. 1) How to subdivide the ship with transverse bulkheads and predict this effect in view of damaged stability at the initial designing stage. 2) Haw to devide the ship longitudinally with tank top, intermediate decks, longitudinal bulkheads and/or partition walls, considering the damaged stability. 3) How to treat the transient condition of tank top flooding which seems to be the worst condition of flooding.

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A new method to predict hydrodynamic forces acting on semi-submersible drilling units is proposed. A simplified Green's function is used to solve the boundary value problems where the wave lengths of incident waves are assumed to be significantly larger than the cross-sections of the structual elements. It is found that this method is more useful than both the strip method and the three-dimensional source distribution method which have been used to predict hydrodynamic forces acting on semi-submersible drilling units so far. Because the present method takes the hydrodynamic interaction effects into account together with the other structual elements, it improves the accuracy much more than that of the strip method. On the other hand it decreases the computing time much less than that of the three-dimensional source distribution method. In order to confirm its validity for radiation forces and wave exciting forces, the results obtained by the present method are compared with those obtained by the three-dimensional source distribution method and the experimental ones. It has been made clear that the present results are in good agreements with the theoretical ones and the experimental ones.

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This paper is some considerations of "Tsunami" which causes ships damage in the eastern coast of the Japan Proper. There are two wave systems. The one occures before earthquake or land-slide in the ocean. This preliminary tremor preceeds about 6h03m-8h14m before the second main solitary wave system apperes. The typical seismological travelling velocities are listed as follows: (1) Predictive wave 7.4007, 4.0667, 1.4458, 0.1917km/sec. (2) Main wave 7.4007, 4.0053, 1.4458, 0.1917km/sec. In the above table, we notice the same value of sonic velocity in the water of 1481.5m/sec and also the same "Tsunami" of 204.8m/sec. Progressive wave propargates with energy supply from the bottom of ocean.

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Manufactured by thermo-mechanical control process acclaimed as revolutionary for turning out the 50kgf/mm^2-class high-tensile steel, what is called TMCP type 50kgf/mm^2-class high-tensile steel has come to find prevalent applications as ship hull steel. This report reviews the results of a study the authors performed on fatigue strength of welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel, which may be encapsulated as follows. (1) The S-N_f diagrams drawn for high heat-input butt-welded joints (with reinforcement weld) and fillet-welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel show no differences, for practical purposes, from those obtained for the similar joints in the 50kgf/mm^2-class high-tensile steel manufactured by conventional rolling process. (2) Likewise, fatigue crack propagation taking place in HAZ of high heatinput butt-welded joints produced in the TMCP type 50kgf/mm^2-class high-tensile steel shows no differences in characteristics from that which takes place in HAZ of middle and high heat-input welded joints, of the 50kgf/mm^2-class high-tensile steel manufactured by conventional rolling process.

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Taking up the TMCP type low-temperature carbon steel plate (equivalent to SLA33B and SLA37 steels) and the TMCP type low-temperature low-Ni steel plate (equivalent to SLA37 steel) recently developed for practical use as new structural steels, this report discusses the strength properties of these steels with an emphasis on fracture toughness of the base metal as well as of the high heat-input welded joints therein produced, the gists of which may be encapsulated as follows. (1) Articulating excellent strength properties of the TMCP type low-temperature steel plates, the authors make a point among others of the extraordinary brittle crack propagation arrest characteristics of the steels. (2) The authors endorse adequately high toughness offered by high heat-input welded joints of the steels even at temperatures of as low as -50 to -60℃. (3) Also, the authors confirmed that the steels can fully be used for such heavy structures as cryogenic LPG storage tanks, north-sea marine structures, etc.

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When a ship bends in still water, the distribution pattern of bouyancy will change. This change causes to reduce the loads acting on the hull girder. The effects of this change upon the longitudinal strength of a ship will be small so far as the ship bends slightly. But, the larger is becoming the deflection of hull girder, the larger is becoming the effects of this change. In this paper, the authors idealize a ship in still water as a beam set on the elastic foundations. And we try to estimate the effects regarding a tank ship of Floating Oil Storage Barge System. And also, we investigate the effects of thermal deformation of hull girder due to temperature differences in a cross section. As the results of this study, we obtained the following items; (1) The change in distribution pattern of buoyancy due to deflection of hull girder reduces the value of the maximum bending moment about 26%, in this case. (2) Taking into consideration of thermal deformation, this reduction will become larger assuming that the temperature of deck side is higher than that of the bottom side.

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