Paper is aimed to study analytically the steady characteristics of the fully cavitated hydrofoils by acceleration potential concepts. By taking the usual linearized assumptions, the problem can be reduced by Tulin transformation to potential one of mixed boundary type. Basic integral equation with respect to acceleration potential, resulted from the boundary condition over the hydrofoil, is of Sohngen's type. After examining the behaviour of singularity of pressure at the leading edge from the acceleration potential obtained, the lift and drag are expressed in a form of Munk's integral. Then it is shown that the present method of analysis can be easily extend to the fully cavitated hydrofoils with upper and lower free boundary of practically extreme importance.
Numerical calculations are made for the fully cavitated hydrofoils with upper free boundary and the effect of upper free boundary on the steady characteristics are examined in some detail. Comparisons with experimental results confirm the present theory as far as the linearized assumptions hold.

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A linearized theory which is based on Tulin's source-sink method, is used to obtain a solution for the two-dimensional cavity flow past a hydrofoil of arbitrary shape having free streamlines. Expressions for the hydrodynamic coefficients of the fully cavitated hydrofoils are obtained. To check various cavity models, calculations are carried out for a flat plate profile for which an experimental datum is available.

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In the previous paper the author developed the method to calculate hydrodynamically the performance characteristics of propellers in nonuniform flows by using the unsteady lifting surface theory. In the present investigation, applying this method to an example such as Dr. van Manen requested at the 10th I. T. T. C. to carry out tests of the given propeller and wake in various cavitation tunnels, he calculated the hydrodynamical velocities, forces and moments in open water and the nonuniform flow, and made partly clear the essential qualities of propulsion, and further found that existence of cavitation on the blades can be assumed theoretically.

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A linearized theory is developed for obtaining the lift distribution on the wing with low aspect ratio. The theory is based on the assumption that, in the case of low aspect ratio wing, it is rather important to adopt not the projected surface into the plane of free stream but the wing surface itself as the lifting surface than to treat it from the non-linear theory. A linear approximation method useful in predicting the chordwise lift distribution on the rectangular wing with low aspect ratio is deduced from the present theory. The computed results from this approximation are compared with test data and show satisfactory agreement. From this fact, the propriety of the above mentioned assumption is proved. The lifting surface theory presented in this paper may be widely applicable in predicting the hydrodynamic forces on so kind of low aspect ratio wings, because of linearization of the theory.

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It is presented how to solve the ship surface condition of a displacement ship in steady motion considering the free surface effect. The free surface condition is, of course, linearized by the infinitesimal wave height and slope assumption. The theory is developed, supposing that the combined velocity potential of the double model conception and the free wave term will approximate the exact velocity potential in the equation of the ship surface condition. Furthermore, it is assumed that a beam is small in comparison with a length. The author solved the basic integral equation numerically for infinitely deep struts and obtained source distributions involving the free surface effect, which yielded good results of wave-making resistance and wave profiles.

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To investigate the relation between the roughness of hull surface and increase of skin frictional resistance, following procedures. were taken;
i) preparation of a portable roughness recorder, ii) roughness measurements of hull surface of newly built ships and of a ship after 1 & 5 years service, iii) resistance test of steel plates similarly treated as actual ship hull, iv) the same plates were submerged in sea water for 10 to 49 months, v) resistance test of the submerged plates after cleaned and repainted, as ships in docking Main results of the above research are summarized as follows.
a) Roughness of newly built hull are expressed by
H_??_ (3060) λ^0.7,
where H : apparent amplitude in micron.
λ : apparent wave length in centimeter.
b) Roughness configuration of the ship in service and of the submerged test plates are coincident in tendency. From this, the results of our resistance tests can be applied to estimate the augmented resistance of actual ships.
c) Approximate relation between ΔC_fs and ΔC_fm, can be expressed by
ΔC_fs_??_ΔC_fm· (C_fs/C_fm) ²·
where ΔC_f : augmentation of C_f due to roughness,
C_f : frictional resistance coefficient of smooth surface,
“s”, “m” : suffix representing “ship” and “model”.

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The Authors have been investigating into the effectiveness of anti-pitching tanks in reducing pitching motion of ships. The idea is to put openings at the side of fore or aft-peak tanks to let sea water flow in and out at 90 degrees phase lead to the pitching and therefore will result in increase of damping for pitching motion.
Through fundamental researches, the Authors found that the larger the water plane area of the tank the more effective the tank and that shallower the position of the openings the more effective the tank. It was also found that if the openings are attached by ducts of certain length, the tank will be more efficient.
A full scale ship trial was made on a buoy tender HOKUTO of 537. 63 G. T. Fore-peak tank only was provided by under water openings. The waterplane area of the fore peak tank was 1. 7% of ship's waterplane area. The tank was also provided by two air ducts which can be blocked to make the tank inactive for comparison.
Trial data at the opening of Tokyo Bay show that pitching motion was reduced by 30% to 50%. This figure almost doubles the predicted effectiveness of the tank by model experiments. Cause of this discrepancy has not yet been clarified.

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This paper deals with the dynamical stability of a ship equipped with an anti-rolling tank in accordance with the Japanese Standard of stability for ships. That is to say, both in case of C₁ criterion coefficient, (ship, which is going under the condition of steady wind and steady waves, is subjected dynamically to a gust of wind having 1.5times wind pressure of the steady wind when the ship is at the maximum angle of roll windward) and in case of C₂ criterion coefficient (a ship, which going under the condition of steady wind only, is subjected dynamically to the similar gust of wind as in case of C₁ coefficient), the maximum angle of roll is calculated theoretically. Now the present authors suggest how to treat the anti-rolling tank so far as the rule of stability for ships is concerned.
Besides, they have also gotten the maximum angle of roll both theoretically and experimentally in the case when a ship is subjected to an impact force, thereby checking the theoretical calculation.

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The effect of bilge keels on the rolling of a ship depends on many elements such as the area, the width, the aspect ratio, Reynolds' number, the draught of ship, the distance of bilge keel from the centre of gravity of ship, the height of centre of gravity of ship and the form of bilge. It was fouud that this effect is proportional to the nth power of mean velocity of the bilge keel, the index n being influenced by the width of bilge keel, the draught of ship and the distance of bilge keel from the centre of gravity of ship. Taking the above elements into consideration and analysing results of systematic experiments on the bilge keels with two dimensional ship models, a new approximate formula for calculating the decrement of angle of roll due to the bilge keels was obtained.

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The impulse response function, which had not been used so commonly in ship response, has come to be rather oftenly discussed in these days. This author has written about the usefulness of that function, and made clear the possibility of getting this statistically from the response in rough sea, through correlogram analysis. Here an example of this method is shown and the merit and the demerit of this method is considered.
Secondly, the effect of nonlinearity of the response system on the computation of spectrum and the response function is estimated through an approximation method. The character of the truncation of the spectrum by this effect is introduced, and an example in rolling with square damping is shown.
As an Appendix, the data processing scheme for the estimation of the frequency response of a ship are summarized from an effort to standardize the statistical analysis of frequency response function of a system.

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It has been shown by Ursell [1] that there are prisms of certain sections which do not create waves when they roll in a still water surface. This problem has been extended by Bessio [3] in motion of six degree of freedom. On the other hand, Newman [4] has shown making use of Haskind relation that damping coefficient for any motion of a body is directly related to the exciting force acting on the same body in waves.
These results indicate that there must be bodies which will not be acted by any exciting force by waves.
In this paper, the Authors delt with this problem restricting it to the case of heaving and pitching motion. It has been shown by Motora [5] that heaving force acting on a body in waves is.approximately expressed in the following form :
F_ZW=γ₁K_ZρVZ_W+γ₂N_ZZ_W+γ₃ρgAZ_W
where γ₁, γ₂ and γ₃ are correction factors which are the functions of wave number K=ω²/ g
K_Z is the added mass coefficient of the body for heaving
V is the volum of the body
Z_W is the surface elevation of waves
N_Z is the damping coefficient
ρ is the density of water
g is the accerelation of gravity
A is the water plane area of the body
The first term shows the body wave interaction and the third term shows the Froude Krylov force with Smith Correction. Since Z_W=-ω²Z_W, it is clear that the first term of the right hand side of the equation is reverse in sign compared to the third term. In the case of usual ship forms however, in significant frequency range, the first term is not so large compared with the third term.
However, if a section form of a ship is designed so that the first term is comparable with the third term at significant frequency of waves, those two term will cancel each other and only the second term-the damping term-will remain.
On the other hand, Newman's relation shows that the damping coefficient is proportional to the square of heaving force which is now very small. Therefore, it is possible to make the heaving excitation practically zero at specified frequency of waves.
In this paper, the Authors showed some examples of such forms and the measured heaving exciting force. Though only results in two dimensional problem were shown, this problem can be extended into three dimensional problems.

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There are special ship-like forms having no radiating wave when they oscillate and this means that they have no wave-damping force and that receive no exciting force from the on-coming wave.
This paper gives the variety, the properties of and the method to obtain such forms when they have no advance speed.
In general, they seem to be not very practical shape except the ones in the rolling motion and the one not completely but in one component wave-free which may receive no exciting force from the on-coming wave but have the wave-damping force.

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This paper relates to some model experiments in respect to shallow water effects upon turning ability which were carried out at the Ship Research Institute under co-operation of the Sasebo Heavy Industries Co. Turning tests were carried out for two model ships, one of a cargo ship (L/B=7.3 B/d= 2.5C_b =0.7) and the other of a mammoth tanker (L/B= 6.41 B/d=2.61C_b=0.81), at various water depth. These tests show that shallow water effect upon turning ability increases slightly in accordance with decrease of water depth, while the depth is deeper than about 2.5d, however increases remarkably when the depth decreases less than 2.5d. For example, the non-dimensional angular velocity, Ω, for 35° helm angle, at water depth of 2. 5 d, is equal to 9095% of the Ω for the same helm angle at deep water, however at 1.3 d, the Ω is equal to 5060% of the Ω at deep water for the same helm angle.

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The present paper shows some hydrodynamic coefficients for correcting the mass of cargo oil or the liquid load in a tank with free surface in estimation of the natural frequency of ship vibrations. The apparent mass of liquid cargo in a ship vibration will be calculated as virtual mass of the liquid performed inside cargo tank under consideration. So that, it will be expected that the.apparent mass depends on the cross section of cargo tank and the direction of vibration.
As an example, the results were presented as the ratio of apparent mass of perfect fluid with its frozen mass which filled a half in the tank of an elliptical cross section in vertical, horizontal and torsional vibrations of ships hull. It is to be noted that the apparent mass ratio and mass moment of inertia ratio are obtained less than unity in the horizontal and torsional vibrations respectively, whereas the ratio is calculated as unity in the vertical vibration. The effects of the vibration of bottom plate of the tank of rectangular cross section upon the effective mass of general cargo and fluid in the tank which is vertically vibrating were also investigated. The apparent mass ratio in this case is greater than unity when the vibration of bottom plate is inphase, on the contrary the ratio is less than unity in the case of out of phase of bottom vibration. The, apparent mass ratio of the liquid cargo is some more less than that of general cargo in the case of antiphase of bottom vibration.

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Systematized method of application of energy principles to the bending, vibration, and buckling problems of elastic plates with arbitrary shape and arbitrary boundary conditions is presented in this paper. Focusing attention to the free lateral vibration of plates, the method of application of energy principles to various plate problems are explained with several numerical examples.

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A couple of years ago, one of the authors presented a paper entitled “On the Influence Surfaces of Orthotropic Plates” and last year he has also puplished another report on the same subject from his research institution. His studies so far has been concentrated to the design problems of orthotropic plates under lateral loading. Through his recent study on the thermal stress problems of plates, however, he has found that use of various influence functions of plates will be very effective in research on the initial stress problems of plates such as residual stresses and thermal stresses.
In this report, two classes of new influence functions are introduced and their fundamental relations are discussed. With several simple examples, the method of application of those new influence functions to initial stress problems will be briefly indicated.

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This investigation considers the problem of deflection and strength of the rectangular plate with elastic hinges and splits under general distribution of loading, and under the boundary conditions in which one pair of opposite edges normal to the direction of elastic hinges and splits are simply supported, the other pair of edges are elastically supported or elastically built-in.
We express the influence of elastic hinges on the rectangular plate in impulse function of 3rd order, and that of splits on the plate in impulse function of 4th. order. And we apply double finite Fourier Transformation to solve the equation of equilibrium of the rectangurar plate under the above boundary conditions.

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The phenomena of underwater explosion and the damage mechanism due to explosion have already been investigated quite well by many researchers.
It seems, however, to the author not yet being well discussed both the quantitative measurement of water pressures due to effects of expansion of successive gas globes and damage amounts.
In order to make one part of these unknowns above explained clear, the experiment of cylindrical shells due to underwater explosion has been carried out, and these cylindrical shells were made of mild steel or high strength steel and stiffened by inner frames with different span lengths.
After hanging the cylindrical shells by wire ropes at the depth of 30meters under the water on the about 1, 000meters depth sea, the explosion tests were pursued by blasting the TNT spherical explosives from either the bottom or side shell, yielding to the small and large damages on shells.
This paper is mainly concerned with small local damages happened between frames, and hence the large ones were disregarded.
Comparing both results of experiments and calculations on water pressures and displacements, the semi-empirical formulas of time lag among peak pressures due to gas globes and the amounts of maximum concavities of damages on the cylindrical shells were determined, and good coincidences were obtained between calculations and experimental results of the large cylindrical models of 5.5meters diameter made of mild steel, which were already carried out about 20years ago.

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A theoretical studies are presented for the some problems of shell instability of circular cylindlrical shells subjected to hydrostatic pressure. The method used is that of minimumization of the total potential.
(1) Effect of frame on shell buckling
The deformation of the shell immediately befor buckling was assumed to be uniform by previous investigators. But the deflection prior to buckling is not uniform owing to the effect of the frame on the deflection, it is the axisymmetrical deformation. The buckling pressure occured from this axisymmetrical state is calculated.
(2) Effect of buckling configulation
An axitial distribution of radial displacement during buckling was given by Q=cosπξ in many previous papers. But it may be thought that buckled wave pattern is more flat form than cosπξ by the effect of tangential stress existing in the shell, then the buckling pressure obtained by putting the buckled wave pattern as follows
Q=A sinh κ₂ξ sin κ₁ξ+Dcosh κ₂ξcos κ₁+K
is compared to the pressure in the case of the pattern given by cosπξ.
(3) Error of approximate formula of buckling pressure
The approximate formulas of buckling pressure developped from Mieses' accurate formula by Tokugawa or Windenburg are used generally for the disign and checking of experimental data. The accuracies of these formulas are examined, and checking of experimental data by Mieses' formula are proposed.

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Studies on the plastic design of plane structures subjected to in-plane-load have been performed by many reserchers, and the collapsing loads and mechanisms may be obtained easily in most cases.
The minimum weight design methods of such structures have been also established.
If the plane structures, however, are loaded outward direction of their plane, they may crash in three dimension. To analyze this problem we must use the yielding condition of the sections which sustain simulteneously two bending moments and a twisting moment therefore the analysis becomes difficult.
A few studies are reported on the problem, but they contain only numerical or experimental results of sepecially fixed models and the general solutions are not considered. A pair of king posts is one of the representative plane structures which will collapse spatially. The authors studied the plastic design method of the structures that are loaded perpendicular to thier plane, using the linearlized yielding condition for combined bending and twisting moments introduced by Hodge and Sankaranarayanan. The relations between the collapsing loads and mechanisms, the dimensions of posts and the shapes of sections are obtained systematically.
Then we considered the optimum design condition from a view point of weight saving and showed a minimum weight design method for king posts.

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In a cross section of a beam where no shear force exists the normal stress distrilution is rectangular at the fully plastic state under the assumption of perfect plasticity of material. Under the existence of shear force the normal and stress distributions are somewhat complicated which must satisfy conditions of equilibrium, yielding and compatibility. By approximating these distributions of normal and shear stress by rectangular ones which satisfy yield condition, rational results are obtainable.
In this paper the interaction between the plastic moment and shear in I-section beams with cutouts is treated under the assumption of rectangular distributions of normal and shear stress and the interaction curves between the shearing-bending ratio r= S /S₀/M/M₀ and the plastic moment Si Mo coefficient m=M/M₀, at several opening ratios of cutouts, are obtained concerning three types of I-section. And using these interaction curves, the equistrength opening ratio κ, within the bounds of which the cutout dose not at all weak down the collapsing strength of the beam, is obtained as the function of longitudinal position on a few beams with typical end condition and load condition.

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The characteristics of both fracture stress curves, cleavage and fibrous were investigated in regard to their dependences on temperature and stress-triaxiality.
Used for experiments are a killed mild steel and high tension steel. As the results of the experiments, the following important informations are clarified.
(1) The cleavage fracture stress curve is hardly affected by changes in temperature and stress-triaxiality as shown in Fig. 4.
(2) The fibrous fracture stress curve is remarkably sensitive to those changes as shown in Figs. 7 & 9.
(3) The condition for fibrous fracturing is identically represented by one stress curve regardless to the degree of stress-triaxiality, in case where the octahedral shearing stress and strain (τ_oct and γ_oct) are used, as shown in Fig. 11.

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The present authors have investigated on brittle fracture initiation in welded structures, using 600mm wide, transversely butt-welded plates of 80 kg/mm² class high tensile steels.
They found that brittle cracks initiated at fusion zone of one surface, and immediately propagated through the heat-affected zone. Fracture stresses, in some cases, were lower than yield stress of the base metal.
Such brittle fracture, occuring along the brittle zone of welded joint at low stress level, was considered to be a characteristic phenomenon to welded structures; it could hardly be reproduced. in any of the existing testing methods.

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It is well established that contraction on welding results in plastic strain and residual stresses of yield point magnitude in and around any welded joint. Although the magnitude of these residual stresses may be reduced by the low-temperature stress relieving treatment and the principles and applications of the method have been described in a number of papers, but still there is a divergence of opinion on its effectiveness.
Many factors influence the effectiveness of the application of the method. Therefore, one analytical approach to this problem is presented in order to clarify certain optimum conditions that : will give a desirable stress distribution in reducing the residual stresses in the weld to about zero value without imposing any undesirable stresses elsewhere. The theory used herein is described in the previous reports. For simplicity and clarity, longitudinal residual stress pattern. developed by butt welding of two plates is assumed stepwise. Then, the stress changes during thermal stress relieving cycle are analyzed using dimensionless parameters. From the final results, , the optimum conditions to give the desirable stress distribution can be determined very easily.
It is shown that the heated band width is most important factor and if a strip of width somewhat greater than half of effective width of a plate is heated symmetrically to a uniform temperature which is determined by use of formula (9) or (29) and then water cooled rapidly, almost : complete stress relief is realized. However, the effectiveness of such treatment is diminished by the notable hardening of the material in and adjacent to the welded joint.
Some experimental verifications are good in accord with the results of the present theory.

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In this report, three problems of hull deflection during construction will be dealt with. First the deflection of that part of the vessel's bottom which overhangs port & starboard of the concrete building berth will be discussed. Secondly the deformation of superstructure decks during the completion of work after launching will be discussed.
The third and major topic of discussion will be the problem of the deformation of the vessel's bottom and inner bottom in way of machinery room in connection with the problem of propeller shaft centerline alignment and/or boss boring. In regard to this problem, the following findings will be shown :
(1) The rate of rising of the stern is greatest during the earlier period of construction and decreases gradually as the work progresses. The amount of eccentricity of stern tube bossing when ploted against progress of work gives the “Sine” curve.
(2) The athwartship deflection of the vessel's stern either to port or starboard is strongly influenced by seasonal, climatic conditions.
(3) The fore & aft shrinkage of the stern part of vessel's hull is greatest during early stages of construction (as is the case of the stern rising). The rate of shrinkage of the main deck does not necessarily coincide that of the vessel's bottom.
Finally, the shrinking force resulting from welding and heating will be discussed together with the result of some experimental model tests to confirm the fact that the fore & aft shrinkage of the vessel is caused to far greater degree by the welding on the ship's bottom and its vicinity than the welding on the main deck and above.

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J. N. R. has been building 6 new Tsugaru-maru type train ferries which ply between Aomori and Hakodate. In the launching of these ferries, the bending stresses and the deflections of hulls are measured dynamically. At the same time, draft distributions, vertical acceralations, water pressures at the bottom of hulls and the distance of travels, which are necessary to calculate the hull bending moment at the moment of lift by the stern more accurately are also measured dynamically. The means to measure dynamical deflection of large ship has been developed by the author for the first time. Those means of measurements and the cautions which must be taken in using those means are described.

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This study, continued from the previous one, deals with the interference of cranes as a problem of queuing.
This time we changed one of the assumptions into that the cranes have the process of moving as a part of their services so that the result can be use for the more practical application. These results are shown in Fig. 7 and Fig. 8, In these diagrams n expresses the average number of work waiting for their receiving services (including those which are being served) and ρ means the working ratio. Then in Fig. 7, for example, the case N=3, d=0.1l…, represents the case of three cranes whose winding-down positions are selected at random within the range of 10% of whole working length from their winding-up positions, and in Fig. 10, the case N=3, d=0.1l, …, for example, means the case of three cranes and when a crane is giving a service it occupies the range of 10% of whole working length from its winding-up position and any other cranes cannot enter this range. These diagrams, Fig. 7 and 8, can be applied to the practical use when we want to know the effect of installing more cranes or when we look for the difference of effectivity by changing the principle of cranes' services. We also stated here on the way to decrease the interference of crances.

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It is well known that a submarine has the excellent propulsive performance in high speed. navigation in deeply submerged condition, but few papers have sufficiently shown economical feasibility of submarines for commercial use.
The authors have studied about the feasibility of submarine tankers with a view to develop technical problems of commercial submarines. At first, the experiments on five submarine tanker models with the circular and rectangular hull sections were performed by method of three-component measurements at Mejiro No. 2 Tank.
Examining the resistance, stability, floating draft and general arrangement of the submarine tankers, the authors chose the ST-2 type rectangular hull form as best for the submrine tanker. The lines of the ST-2 type hull form was shown in Fig. 3
The ST-2 type submarine tankers with various dead weights and shaft horse powers were designed and their investment, operation cost, annual profit, freight rate per dead weight and capital recovery factor were calculated. The results of this study were summarized in Fig. 19 to 23. The best submarine tanker in the point of view of commercial feasibility was 40, 000 tons in dead weight and 20, 000 horse powers in shaft horse power under restrained condition within 14 meters in maximum floating draft. On the contrary to the previous opinions, was shown the fact that the submarine tankers would not be very fast than present conventional tankers. As shown in Fig. 23, the submarine tanker would not have commercial feasibility without drastically decreased cost of nuclear power plants.

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This paper deals with the results of tests made on the divided and confluent flow at the branch part of the special type tee fitting for a rectangular air duct. As the results of experiments, the empirical formurae for the coefficient of resistance in the confined two streams in the rectangular air duct have been obtained.
(1) Loss in the divided flow at the branch part.
upside type fitting P=0.9Hm+1/3Hb flank type fitting P=1.5Hm-0.79√Hb·Hm+0.11 Hb
(2) Loss in the confluent flow at the branch part.
upside type fitting P=-0.6Hm+1.4Hb flank type fitting P=-0.4Hm+1.0Hb
Where
P=pressure loss, mm WG
Hm=velocity head in the main duct, mm WG
Hb=velocity head in the branch duct, mm WG
b=breadth of the main duct, mm

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The airborne and solidborne noise measuring equipment, small in size and light in weight was especialily devised for ship, and various tests have been made for practical use.
Using this equipment, noise and vibration measurement were made by several types of ship on their trial navigations. The results of observation about the noise source, spectrum and the calculated loudness will be summarized as follows;
1) The relation between the calculated loudness of noise (Loudness Level, Perceived Noise Level, Noise Rating Number) and A, B, C, sound level were established and the results showed that good correlation was obtained between the calculated loudness and the A sound level calculated from the original noise spectra.
2) The judgement of ship. noise will be made by using the calculated regression lines or more simply by adding the value of 8 (LL), 15 (PNL), and -3 (NRN) to the indicated A-sound level, so the ship noise shoud be measured by A weighting regardless of noise level.
3) In accommodation spaces, the noise, largely solidborne, has a spectrum that slopes off approxim ately 5 dB/oct with increasing frequeny and the A sound level is about 70±20 phon. In engine room, however, noise has more energy at middle and high frequency and the level is nearly 95±10 phon.

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Multiple diesel engine systems combined with several medium-speed engines have been recently developed as a propulsion system for ocean-going vessels.
If bunker oil can be used satisfactorily as a fuel for these medium-speed engines, the operation cost of ships would be more reduced. However, the test of bunker oil as a fuel heated up to high temperature has not been examined yet for this type diesel engine by this time.
This paper describes experiments to investigate the effect of fuel temperature on combustion for diesel engines.
The results present that the fuel consumption and the exhaust temperature of the engine are increased with raising fuel temperature up, on the contrary of the authors expectation.
An analysis is also made of these results.

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