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Article type: Cover
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Cover1-
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Article type: Cover
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Cover2-
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Article type: Appendix
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App1-
Published: June 30, 1978
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Masatoshi BESSHO, Yusaku KYOZUKA, Shoji IIDA, Akira HIDAKA
Article type: Article
Pages
1-6
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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This is a preliminary research on a sea surface sweeping ship with large openings at bow and midship and having an open channel in the ship. The sweeping performance of such a ship may be represented by her sweeping area in a unit time, and the area must be her sweeping breadth multiplied by the speed. Theoretical consideration on the sweeping breadth shows that it is proportional to the root of flux of water flow in the channel and that the sweeping area is proportional to ship speed. The model experiments are carried out, the sweeping breadth are measured in various cases, compared with the theoretical prediction and the correspondence is fairly well.
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Tomoo HANIWA
Article type: Article
Pages
7-16
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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A geometrical method of designing hull form of ships in the speed range of Froude Number, 0.21∼0.34, is presented continuing previous report, where the values of Cp, Cw and displacement-length ratio are given as design requirements. The method consists of the following procedure. (1) A shape of Cp curve of fore body is given based on elementary wave theory, and a proper size bulb is fitted to main hull. (2) Based on separability hull principle, the length of middle body for maintaining the designed displacement is determind corresponding with the values of designed C_<PF> which is selected by the theory. (3) The shape of Cp curve of aft body is drawn up while modyfing the same curve of Type Ship, taking the viscosity resistance and propulsive efficiency into considerations. (4) The geometrical method of deforming hull form such as a method of 1-Cp and logarithmic ordinate is applied in present report for practical using. The Cp curve drawn up by present method is closely resemble to the same curve of actual hull form, of which the result of tank test is valued higher.
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Kosaku TAJIMA, Yoichi KUROYANAGI, Hisayoshi TATANO, Yasuo YOSHIMURA
Article type: Article
Pages
17-28
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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This paper treats many manoeuvring test results of three 360,000 DWT sister tankers and their model for studying scale effects of ship manoeuvrability. A new, sea trial measuring device, "TRIPOSIK", played an important part of the study. The device, which consists of a main station transmitting UHF radio waves on board and two slave-stations on shore, is ideal for measuring a ship's speed and its position. Even though the full scale ship showed slightly larger ∣r'∣ values than the model in large helm turnings, course keeping qualities were almost the same for both of them. Drift angle, speed drop ratio, advance and transfer in each steady turning were measured with good accuracy. The authors succeeded in obtaining a good method for simulating propeller-reversing stopping ability. A pair of differential equations for the purpose is; [numerical formula] [numerical formula] By solving these equations the path and speed after the propeller is reversed can be accurately simulated. Other factors such as head reach, lateral reach, stopping time and heading angle at zero advancing speed also coincided well with observed ones. Through these facts, it might be said that this method is not only useful for these ships but also can be applied for any other ships which have a conventional propelling system.
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Tatsuo KASHIWADANI
Article type: Article
Pages
29-39
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Some of full-bodied ship models are unusually stable on course and others are unstable despite of almost same principal dimensions. This difference of course stability is caused by difference of hydrodynamic forces. The author measured the hydrodynamic forces of two typical models; one is unstable and another unusually stable. In the previous paper he assured that the difference of course stability was caused by the difference of hydrodynamic damping acting upon the aft-body. In this paper this difference of hydrodynamic damping upon the aft body is examined employing the surface pressure measurement, the flow survey in the wake field and flow observation on aft-body surface. From these results the following conclusions are obtained; The difference of hydrodynamic damping is due mostly to the difference of pressure acting aft of the s.s. 2 in bare hull condition. The difference of hydrodynamic damping is due to the difference of the stern flow in which the trailing vortices generated at the bilge part near the s.s. 2 play an important role. A remarkable flow named "reverse lateral flow" was observed between stern over-hang and propeller race, which flows from back side to face side against the general flow direction. The effect of such flow is not clear enough yet but certainly it has some concern to the empirical formula between the course stability and the stern profile of full-bodied ship models.
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Omar M. M. KHATTAB, Kensaku NOMOTO
Article type: Article
Pages
41-55
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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In this study we apply the transfer function approach to the steering control of a ship in canal. The directional stability in a canal and the effect of the canal dimensions on the behavior of a ship are studied in details. Also we analyse the automatic steering in a canal; the effect of control gain parameters on the response are studied by Nyquist criterion, eigenvalue analysis, and by calculating the time history. The behavior of a ship in a canal can be stabilized without oscillation by proper combination of heading and position control. Also we find that, the ship motion in a canal can be represented by a simplified mathematical model, i.e. second order differential equation. The parameters of the simplified model are determined by fitting the model to the ship motion obtained by the exact mathematical model, i.e. the original equation of motion.
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Masataka FUJINO, Atsushi KIRITA
Article type: Article
Pages
57-70
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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It is well known that the ship is forced to deviate from her course when it is decelerated by rotating her propeller in the adverse direction. This paper clarifies the characteristics of unbalaced hydrodynamic forces caused by the propeller running astern when the ship has forward speed. First, the influences of ship speed and number of revolution on the quantitative and qualitative characteristics of unbalanced hydrodynamic forces are examined by model tests, when the ship travels in a straight course without sway and yaw motions. Secondly, the effects of sway and yaw motions are discussed according to the experimental results by the circular motion tests. As a result, it is concluded that when the ship has no transverse motion, unbalanced hydrodynamic forces can be regarded as a function of J_P(=U/nP) and the effects of transverse motions can be expressed well by an equivalent sideslip velocity v'_s at the stern defined by v'-r'/2. Lastly, the course stability of ships while stopping by adverse rotation of propeller is discussed. Our conclusion that the strong race of propeller with adverse rotation makes the ship more unstable coincides with the experimental results obtained by Wagner Smitt and Chislett in 1972.
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Hiroshi ISSHIKI, Mitsunori MURAKAMI
Article type: Article
Pages
71-82
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Just before undocking of a ship, there occured an accident that the mooring rope was cut off because of an abnormal surge motion of the ship. The cause of the accident has not yet been clarified, but there is a possibility that a wave incident from an open sea induced such an abnormal ship motion. In this paper, the surge motion of a ship freely floating in a dock is discussed. As the result of the study, the existence of a resonant frequency for the surge motion is shown with some numerical examples. Because of the insufficiency of the present study, the above mentioned possibility is not still confirmed.
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Hiroyuki SADAKANE
Article type: Article
Pages
83-93
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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In this paper, we direct our attention to fluctuation of the apparent weight of a ship who rolls among regular heavy waves. Fluctuation is usually ignored because of the supposition that waves are gentle. But it is considerable in amount is waves are heavy. It exerts significant effects upon the ship rolling and brings interesting features on her behavior. We examine the features experimentally by model tests on a navipendular or on water tanks and theoretically by solving the rolling equation of the type [numerical formula]. In this equation, θ_a = the relative angle of heel, K = the coefficent of damping, ω_0 = the natural circular frequency, M, β = the characteristic coefficients representing non-harmonic character and Mω^2sin ωt=the external force. To solve approximately the equation, we make use of the averaging method under the assumption that the solution may be expressible in a form of θ_a = A sin (ωt-ψ) + B sin (ω't-ψ').
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Hiroshi ISSHIKI
Article type: Article
Pages
95-103
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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The estimation of motions of a floating body in waves is one of the most important problems to assure the safety of ships and various marine structures, and much study has been done using various methods. This paper discusses this problem from the viewpoint of the Hamilton principles in mechanics. In case of a steady irrotational flow of an incomplessible and invicid fluid, there exist variational principles called as the Kelvin and Dirichlet principles. The existence of the similar principles can be shown for water wave problems. In this paper, not only the fluid motion but also the motion and elastic deformation of a floating body are covered within the variational principles, and mechanical system consisting of a floating body and a fluid is discussed in a unified manner.
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Hiroshi ISSHIKI
Article type: Article
Pages
105-116
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Ships and offshore structures make complicated motions in waves. The estimation of their motion is very important to assure their safety. Many methods have, therefore, been developed to discuss the motions of a floating body. In this paper, methods based on variational principles are discussed. A irrotational flow such as water waves of an incompressible and invicid fluid can be dealt with in a unified manner using variational formulations derived from the Hamilton principle. In this paper, the mutual relations of these variational principles are discussed in detail. And the radiation condition of diverging waves is also introduced in a reasonable manner.
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Takaichi SOMEYA, Shoichi NAKAMURA, Kimio SAITO
Article type: Article
Pages
117-126
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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Following the previous report, the hydrodynamic impact pressure on the forward flat bottom of a full form ship in waves has been studied. In this report we assume that the two types of impacts may be occured depending on the relative angle between ship bottom and wave surface at the moment of impact. One is the so-called Wagner type impact and the other is the Bagnold type impact which will be accompanied by the trapped air between the ship bottom and wave surface at the moment of impact. The results are summerized as follows, 1) From the drop tests onto the calm water, it is shown that in the case of Wagner type impact the maximum pressure acting on the two-dimensional model may be proportional to the square of the impact velocity, whereas in the Bagnold type impact it may be proportional to the impact velocity. 2) The occurence of the two types of impacts in waves can be classified by the sign of the relative angle at the moment when ship bottom touches on a wave surface. 3) The Bagnold type impact causes a severe impact acceleration, and its effects will have to be taken into account in the problem of whipping. 4) The occurence of the Bagnold type impact increases drastically in case of shallow fore draft, when it is less than 3%L.
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Tatsuo TSUDA, Sekio KONISHI, Seiichi ASANO, Kazuhiko OGAWA, Kazuyuki H ...
Article type: Article
Pages
127-136
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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In sel f-propulsion test of large tanker models, the characteristics of the model propellers seem to be affected by laminar flow separation on the propeller blade. In consequence, the results of such self-propulsion tests often show peculiar features, especially in the relative rotative efficiency ηR, considerably declining at low Froude numbers. In order to eliminate this laminar-flow effect, an attempt at applying the following three kinds of propellers to self-propulsion models was made by the authors: (1) low-pitch propellers (2) a wide-blade propeller (3) propellers with turbulence stimulators. Moreover, some investigations on propeller open-water characteristics and some flow-visualization tests of the propeller surface flow were conducted. The results of the investigations are summarized as follows: (1) The boundary layer on model-propeller blade is a laminar-flow in substance up to at least ND^2/ν=8×10^5, and three-dimensional separation takes place before ordinary transition from the laminar boundary layer to the turbulent one occurs; needless to say that the flow is turbulent downstream from the separation line. (2) It cannot be expected that the favourable results are obtained by using the low-pitch propeller and the wide-blade one in the self-propulsion tests. (3) In order to make the flow over the blades turbulent, turbulence stimulators are required.
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Masahiko MORI
Article type: Article
Pages
137-147
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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It has been important to measure the wake distribution within a propeller disc for the evaluation of a hull form through the flow phenomena around the hull, and, in consequence, the wake measurement has been actively executed as a routine test. It has been also important for a naval architect to proceed the initial design for which some behaviours of a propeller in non-uniform wake and their troublesome effects on a ship should be taken into consideration. The author presents a practical method to analyse and compile the experimental records of wake distribution and to be useful for the initial design of hull form and propeller. The method consists of three parts; (1) how to axially convert the tangential component of wake through the advance coefficient of propeller. (2) how to macroscopically analyze the wake distribution through some indices which are obtained form the maximum, minimum and mean values in the circumferential variation of wake, and (3) how to microscopically analyze the wake distribution through Fourier analysis. The method will serve to recognize the maximum limit of main engine output and propeller diameter which are allowable for the designed ship, to select the geometrical properties of propeller which are adaptable to the wake distribution, or to select alternatively the turning direction of propellers of a twin screw ship.
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Masatoshi BESSHO
Article type: Article
Pages
149-156
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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There exists a displacement potential of which derivative gives approximately a displacement of water particle from the uniform flow in the water motion around a body. In the steady motion, its derivative in the uniform flow direction is proportional to its velocity potential (divided by the uniform velocity) and its vertical one to its stream function in two-dimensional motion and to the Stokes's stream function in three-dimensional axially symmetrical flow. In the oscillatory motion without uniform flow, it is proportional to the velocity potential. Lastly, in the oscillatory motion with a uniform flow, it fascilitates the formulation of the body surface condition, calculations of the velocity potential and hydrodynamical forces.
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[in Japanese]
Article type: Article
Pages
157-168
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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[in Japanese]
Article type: Article
Pages
169-173
Published: June 30, 1978
Released on J-STAGE: March 30, 2018
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[in Japanese]
Article type: Article
Pages
175-185
Published: June 30, 1978
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Article type: Appendix
Pages
187-189
Published: June 30, 1978
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Article type: Appendix
Pages
App2-
Published: June 30, 1978
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Article type: Appendix
Pages
App3-
Published: June 30, 1978
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Article type: Appendix
Pages
App4-
Published: June 30, 1978
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Article type: Appendix
Pages
App5-
Published: June 30, 1978
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Article type: Appendix
Pages
App6-
Published: June 30, 1978
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Article type: Cover
Pages
Cover3-
Published: June 30, 1978
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Article type: Cover
Pages
Cover4-
Published: June 30, 1978
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