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Published: March 30, 1981
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Article type: Appendix
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Published: March 30, 1981
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Article type: Appendix
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Published: March 30, 1981
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Article type: Appendix
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Published: March 30, 1981
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Article type: Appendix
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Published: March 30, 1981
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Tosiyuki NAKANISHI, Mitsuo YAMAMOTO, Takeo IIMORI, Akihiko OKABE, Masa ...
Article type: Article
Pages
1-9
Published: March 30, 1981
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An under water navigation supporting system for a 2000 m-deep oceanographic submersible ordered by JAMSTEC is described with special emphasis on its acoustic navigation system. The main function of the acoustic navigation system is to locate the mother ship relative to bottom-moored transponders and to locate the submersible relative to the transponders and/or the mother ship. An acoustic navigation technique is used for positioning. The system contains a long base line (LBL), a short base line (SBL), and a super short base line (SSBL) receiver. An advanced technique is applied to the SSBL acoustic positioning receiver : preformed beam technique with 16-element planar hydrophone array. Kalman filter is used for tracking and transponder calibration.
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Michimasa ENDOH, Haruo MIYAMA, Takehiko KUROKAWA, Akitoshi SHIMURA
Article type: Article
Pages
11-20
Published: March 30, 1981
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The propulsion system of the 2,000m Deep Submergence Research Vehicle has been designed to enable the vehicle to have high maneuverability at low speed. It has a main propeller at its stern which is able to be rotated in horizontal plane, and a pair of auxiliary propellers at midship. The direction of the thrust of the auxiliary propellers can be changed horizontally and vertically. The model basin tests, which consisted of resistance and self-propulsion test, propeller open test and the observation of the flow field, were carried out and it was evident that it could get the required maximum speed of 3 kts. These propellers are directly driven by AC electric motors of oil-filled pressure compensated type. The jumbo-transistor inverters are adopted to control the revolutions of these motors. The method of control is by VVVF (Variable Voltage and Variable Frequency), using the pulse width modulation. These inverters are put in a titanium alloy pressure vessel. After the trial productions of AC motor and inverters were completed, several tests were carried out under the conditions of high pressure and normal atmospheric pressure. The adoption of the above-mentioned AC motors and inverters makes the electric system smaller in size and lighter and minimizes the electric power consumption.
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Shoichi OHTANI, Takehiko KUROKAWA, Fuminori KASAI
Article type: Article
Pages
21-28
Published: March 30, 1981
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The electric system is one of the most important subjects in the construction of submersibles. It has a vital role in the entire energy source and all the control signals. The interior and exterior of the personal pressure hull are connected by 14 electrical connectors. Silver-Zinc battery was adopted to the main battery system. Induction motors for propulsion, hydraulic pump, etc. are controlled by jumbo-transistor inverter using pulse width modulation. The circuits are protected by oil-filled N.F.B., oil-filled fuses and over-current relays. The following provides information on the performance and characteristics of this system.
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Minoru OHSUGA, Masahiro HASHIMOTO, Yasumitsu TAKAGI, Koichi NIWA
Article type: Article
Pages
29-36
Published: March 30, 1981
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New energy saving system with the shaft generator motor, which can transfer the electric power between the main shaft and the electric power distribution system, was developed. The first one was installed on a tanker "Yamatogawa" and from the sea trials and the navigation for five months its high performance was confirmed. This system consists of an AC generator motor, a static frequency converter, an electric power distribution system, etc. While the conventional shaft generator system is such that the electric power is only supplied from the shaft generator to the electric power distribution system, in addition to this function, new one provides the capability that the electric power is supplied from the electric power distribution system to the main shaft through the shaft generator motor. This brings reduction in the required main engine output. That is, this system is functioned as a generator when the electric power consumption increases, and functioned as an electric motor when the electric power consumption decreases and there arises a surplus electric power. This system is applicable to various plants for energy saving purpose. In its operation with an exhaust gas turbo generator among others, its advantages can be particulary enjoyed. In this paper, the outline of this system, the results of the trial operation and the operating conditions of the actual navigation are introduced.
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Kenichi ONODA, Eikichi TAJIMA, Yoshio TOGASHI, Michinobu HIROTA
Article type: Article
Pages
37-45
Published: March 30, 1981
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The area where offshore platforms operate has recently spead due to development if the offshore oil drilling and offshore civil engineering technology. This has led to such diverse requirements as the increase of size and the use of platforms under the increasingly severe meteorological conditions. Jacking unit has also come to need a higher jacking capacity, maneuverability and automatic control. So we have undertaken development study on an automatic control system for the tooth and bar jacking unit based upon the experience in constructing and operating SEPs, and have recently completed experimental tests yielding satisfactory results. A control console incorporating electric control circuits, a model jacking unit and a model hydraulic unit were prepared. By carrying out a model test of this jacking unit, we have fully confirmed its excellent performance, safty and reliability.
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Jun OBOKATA, Norio SASAKI, Jitsuro NAGASHIMA
Article type: Article
Pages
47-57
Published: March 30, 1981
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For the design of mooring system and dynamic positioning system of a ship, it is fundamentally important to estimate the external forces induced on the objects. Current force is one of external steady forces, and only few formulas and experimental results for estimating it are presented up to date, besides they are not sufficient to apply to any kind of ships. Authors carried out the obliquely towing experiment for various kind of ship models, spheroids and flat plates to measure the current force coefficients, and showed a new method to calculate current force on any type of ships by means of analyzing our experimental results. In the case of model tests, Reynolds number has to be smaller than actual ship condition, because of towing speed to be restricted in low to exclude free surface effect, in other words wave making resistance. Accordingly, some differences in such current force coefficients between model test and actual ship conditions may exist, and in this paper authors also presented a soiution about that.
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Takanobu YAGI, Ryo TASAKI, Etsuji KAJITA, Kousaku TOMITA
Article type: Article
Pages
59-68
Published: March 30, 1981
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The behavior of oil film around a running ship should be studied for dsveloping efficient oil spill recovery ships. The efficiency of the oil recovery equipment, for instance, largely depends upon the oil film thickness at the position where the equipment is set up in the ship. The law of similitude should be also clarified to investigate the performance of oil spill recovery ships through model experiments. In the present paper, a model is proposed for the mechanisum of flow in oil film due to motion of a ship and validated experimentally. Diamond-shaped models 30cm long were towed in oil films of various thickness in a tank of 150cm(L)×36cm(B)×22cm(d). The distributions of oil film thickness were measured on photograghs taken through the glass side-wall of the tank. The following are concluded from the experiments ; (1) The flow in oil film around a ship is replaced with a supercritical flow in a shallow open channel of the depth equated with the oil thickness in the gravity of gα, where α=(ρ_2-ρ_1)/ρ_1, ρ_1 and ρ_2 are density of oil and water respectively. (2) The behavior of oil film is, therefore, governed by densimetric Froude number, M_0=V/√<gαh_0>, where V is ship speed and h_0 is oil thickness at infinity. The shock waves around models of diamond-shaped water lines derived from the above replacement agreed well with results of experiments. (3) Tests with a geometrically similar model including the oil film can simulate the full scale phenomena when Froude similitude is applied. The geometric similitude, however, usually leads an unrealistically thin oil film in model scale, and then a distortion of similitude is applicable using the different scale ratios in the horizontal and vertical direction.
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Norio TANAKA, Yoji HIMENO, Yoshiho IKEDA, Koji ISOMURA
Article type: Article
Pages
69-75
Published: March 30, 1981
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Experiments for several ship forms in ballast conditions show that the bilge keel effects are unexpectcdly small compared to the case of full load condition. In certain conditions the bilge keels even make no increase of the roll damping for some shallow-draft ship forms. Experimental and theoretical studies using two-dimensional cylinders are carried out to reveal that this is partly because of the wave-damping reduction due to the bilge keels and partly because of the eddy-damping reduction of the bilge keels due to the wave created. The former is caused by the phase difference between the wave created by the hull and the one by the bilge keels, and the latter is caused by the decrease of the relative velocity at the turn of the bilge due to wave generation.
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Hiroyuki SADAKANE
Article type: Article
Pages
77-85
Published: March 30, 1981
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The heeling moment against a small ship, caused by a billow breaking at the crest, is not yet sufficiently investigated. To investigate the characteristics of the billow, and then the dynamical mechanism of the heeling moment, the movements of water particles in a breaking billow are observed in the water tank. From the kinematical analyses of the movements of particles, the experiments on an abrupt water-jet, which is a model of wave breaking, are carried out. These experiments prove the following results, (1) In the breaking region of a billow, the general concept of the effective surface can not be applicable to the heeling moment of a ship. (2) The heeling moment M_q formed by the breaking is impulsive such that is caused by the abrupt water-jet. (3) Strength of M_q depends on not only strength of water-jet but also <KG>^^^-, form and size of a ship.
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Norihiro MATSUMOTO, Keiji SUEMITSU
Article type: Article
Pages
87-95
Published: March 30, 1981
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One model test method by which an actual ship's maneuvering performance can be predicted is the free sailing method. At our ship model basin, the trajectories and yawing angles of model ship were measured during a free sailing model test, and from these values the drift angles of the model ship were calculated. During the analysis, coefficients of the mathematical response model were derived so that simulation calculations could be identified with the time history data of a real ship model test. The proposed mathematical model which includes αr^3 and α_ββ^3 as non-linear terms is as follows.T^'_1T^'_2r^'+(T^'_1+T^'_2)r^'+r^'+α^'r^<'3>=K^'δ^'+K^'T^'_3δ^' T^'_1T^'_2β^'+(T^'_1+T^'_2)β^'+β^'+α^'_ββ^<'3>=K^'_βδ^'+K^'_βT^'_<3β>δ^' The non-linear terms can be presented with hydrodynamic derivatives as follows. α^'≒(N^'_βY^'_<nr>-Y^'_βN^'_<nr>)/C α^'_β≒{-N^'_rY^'_<nβ>+(-m^'-m^'_x+Y^'_r)N^'<nβ>}/C C=N^'_β(-m^'-m^'_x+Y^'_r)-Y^'_βN^'_r We applied this method to a container ship and bulk carrier, and thus confirmed that the method can accurately predict a ship's maneuvering performance.
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Ichiro TANAKA, Toshihiko KAWASHIMA, Yasuyuki TODA
Article type: Article
Pages
97-105
Published: March 30, 1981
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The structure of flow field near free surface at the stern of ship models is investigated experimentally by means of measurement of velocity distribution and flow visualization. It is found that a strong difference exists in flow structure near free surface at the stern between the self-propulsive ship models with a rudder and without it. The difference is characterized by the occurence of a pair of vortices rotating outwardly in the model with a rudder. The physical explanation for this phenomenon is attempted both experimentally and theoretically. Flow visualization by means of air bubble method is carried out for a propeller-rudder system and an asymmetric distortion of flow field is pointed out due to strong interference between the propeller slip stream and the rudder. The result is explained from the standpoint of vortex filaments dynamics.
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Ichiro TANAKA, Yoshito MIHARA, Ken-ichi SAIJO
Article type: Article
Pages
107-115
Published: March 30, 1981
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Four types of two-dimensional viscous flow configurations are solved by a finite element method based on the streamline-vorticity formulation. Galerkin method is adopted. The calculated configulations are the circular cylinder arrays in uniform flow, the circular cylinder in shear flow, the flow in a square cavity, and the flow around a two-dimensional total head tube. All flows are in very low Reynolds numbers.
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Tatsuo TSUDA
Article type: Article
Pages
117-125
Published: March 30, 1981
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This paper presents an approximate method of calculating the laminar boundary layer on a propeller blade. The momentum integral equations have been derived of a rotating blade under the following assumptions : (1) contour of the blade is sector, (2) pressure gradient is arbitrary in the circumferential direction, but is zero in the radial direction. The equations were applied to propeller blade sections at several radial positions separately, assuming that the interraction between the flows of adjacent sections could be ignored. Velocity profiles across the boundary layer were expressed by nth-order polynominal expressions similar to Pohlhausen's method. Numerical solutions were obtained of three kinds of simple rotating bodies and a model propeller. The results of the latter were compared with the flow patterns obtained by means of the oil-film method.
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[in Japanese]
Article type: Article
Pages
127-134
Published: March 30, 1981
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Article type: Appendix
Pages
135-136
Published: March 30, 1981
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Article type: Appendix
Pages
137-141
Published: March 30, 1981
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Article type: Appendix
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Published: March 30, 1981
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Article type: Cover
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Published: March 30, 1981
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Article type: Cover
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