-
Article type: Cover
Pages
Cover1-
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Index
Pages
Toc1-
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Index
Pages
Toc2-
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Naotica NANBA, Thoru SHIMIZU, Nobuhiko WATANABE, Tetsuji HOSHINO
Article type: Article
Pages
1-8
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Submersibles such as Remotely Operated Vehicles (ROV), manned submersible, which have been proven effectively in the fields of offshore oil environment, deep ocean research, etc., are necessary for high maneuverability at low speed. And all submersibles today are propelled and controlled by single dimension devices such as screws, planes. As for Variable Vector Propeller of three dimentional device based on varying propeller pitches both collectively and cyclically, we carried out the model tests on its performance and confirmed its characteristics, which are fairly suitable to the theoretical estimation. By using this type of propeller, it certainly seems to be able to reduce propellers and consquently to contribute to the compactness and the light we light of ROV, etc.. We have been confirming and examining the mecanical characteristics of collective and cyclic pitch changes, controls, etc., and at high pressure, using the experimental model specially manifactured for this purpose. We will report these results in the 2nd report.
View full abstract
-
Shieru NISHIO, Ichiro TANAKA, Hiroshi UEDA
Article type: Article
Pages
9-17
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In the previous report, separated flow field around prolate spheroid at incidence was investigated experimentally and numerically. Based on these results, the separated flow field around ships at incidence is investigated in the present report. In order to confirm and extend the knowledge obtained about the nature and structure of the separated flow field, the measurement of the surface pressure distribution, the measurement of velocity distribution by use of 5-hole pitot tube and the flow visualization are carried out. From experimental results, the characteristics of the separated flow and its relation to the lateral force are discussed. Vortex layer configuration and lateral force distribution are calculated numerically by considering the shedding of vortex sheet, based on a slender body approximation. The comparison between the calculated lateral force distribution and measured one shows the consideration of viscous diffusion and dissipation at the bottom of ships is necessary to obtain the agreement between them.
View full abstract
-
Taketoshi OKUNO, Hideaki MIYAKE, Norio TANAKA
Article type: Article
Pages
19-25
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The boundary layer on the wall surface of the nozzle, the wave suppresser and the channel wall itself affects strongly to the velocity profile of the test section of a circulating water channel. The velocity near the free surface is always smaller than the uniform velocity which is normally determined by the mean value at fairly deep position. In order to obtain the uniform velocity near water surface, the rotor method, a jet-like flow generated by the rotor at the edge of the nozzle accelerates the velocity, is employed here. In this paper, it is shown that at first the two-dimensional wake theory represents the velocity defect near the free surface, and the two-dimensional jet flow theory can be used for representing the flow by the rotor itself. The uniformed velocity profile is obtained by superimposed these two prof les. The optimum rotation number of the rotor is theoretically determined as a function of the uniform velocity.
View full abstract
-
Taketoshi OKUNO, Hideaki YAMAGUCHI
Article type: Article
Pages
27-33
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
This paper describes the results of the application of Laser Speckle Photography to flow measurement. Before flow field measurement, LSP is applied to measure the speed of rotating disk. The specklegram (double-exposured film) obtained by pulsed ruby laser gives Young's fringes which represents the speed and moving direction. The characteristics of laser speckle itself, particularly its size, contrast of the speckle pattern and so on, are examined here for obtaining the clear specklegram. It is found in this case that a high power (about 1J/pulse) pulsed laser must need for flow measurement. The so-called PIV (Partille Imaging Velocimetry), using quasi-specklegram by seeding particles, is of useful technique for practical measurements. The high sensitivity film can be used in this case.
View full abstract
-
Huai-Xin CHANG, Yoji HIMENO
Article type: Article
Pages
35-45
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In order to analyze the three-dimensional unsteady boundary layer development along an oscillating ship form at forward speed, the potential flow computation for the ship form is made in the present paper, neglecting the free surface effect. Hess and Smith's method is used by modifying the boundary condition and the symmetry condition. The unsteady potential velocity due to the ship pitch motion is computed as well as other modes of motion. The results show reasonable agreement with the author's experiments. The calculated hydrodynamic coefficients are of similar tendency to the results of existing calculations using three-dimensional wave-source method.
View full abstract
-
Yoshiho IKEDA, Hiroki YOSHIMATSU, Akira MATSUMOTO, Akira DEGUCHI, Nori ...
Article type: Article
Pages
47-54
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The hydrodynamic forces acting on a model of a high-speed craft fixed by a load cell on a towing carriage are systematically measured for various trim angles, sinkage and forward speed. These data is found to be useful to know the hydrodynamic characteristics of the shape of a high-speed craft. A simulation method for predicting the attitude and speed of the craft for a given thrust force using the measured hydrodynamics forces is proposed. The simulation results demonstrate the effect of the hight of the centre of gravity and the angle of a propeller shaft on the speed of the craft. Measurements of wave exciting forces acting on the model craft moving in regular head waves are carried out. The results show a significant dependency of the pitch exciting moment on the sinkage of it.
View full abstract
-
Yoshiho IKED, Eiji SAKAMOTO, Norio TANAKA
Article type: Article
Pages
55-60
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Viscous force acting on bluff bodies which is started from rest are investigated experimentally. A rectangular prism deeply submerged in uniform flows with different accelerations in circulating water channel, and the force acting on it are measured by load-cell. The experimental results show that the drag coefficient which is obtained by subtracting the potential inertia force form the measured hydrodynamic force depends only on the relative displacement of the body from rest. The lift force and the moment acting on the body which has angle of attack to the flow are also confirmed to depend on the relative displacement. Experimental results for a circular cylinder, a flat plate and a ship model moving laterally show the same tendency.
View full abstract
-
Shigeru NAITO, Makoto UCHIDA
Article type: Article
Pages
61-68
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
To make clear the propulsive performance of a ship in waves, it is necessary to know the characteristics of a propeller in waves. The load acting on a propeller in waves consists of the mean value and the fluctuation. It is well known that in moderate sea the former is same as the load acting on a propeller in still water. On the other hand, the load fluctuation acting on a propeller shaft is composed of that acting on each blade of a propeller. And that acting on each blade of the component caused by amplitude modulation with the wave encounter and the propeller revolution frequency. The side band comnonent of the load fluctuation on each blade doesn't appear on the propeller shaft, because blades of the propell are placed at regular intervals. It is important to make clear the load fluctuation acting on not only the propeller shaft but also each blade of the propeller. The load fluctuation acting on a blade of the propeller in waves had already investigated theoretically, but no experimental verification exsists. In consideration of the above, authors investigated on the load fluctuation acting on a blade of the propeller in waves experimentally. The device to measure the load was devised. And tank tests were carried out under the fundamental condition the the open boat was restrained and the propeller was submerged sufficlenty. The data of the load were obtained successfully.
View full abstract
-
Masami HAMAMOTO, Tadashi OKAZAKI
Article type: Article
Pages
69-76
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The dynamics and control of sway and yaw motions of a ship with combined fin-rudder control system are discussed. In this system, a multivariable controller is used to take into account sway, roll and yaw motions induced by deflections of rudder as well as stabilizing fin for course-keeping and roll stabilization of a ship in quartering seas. A simulation study is carried out to make the comparison between fin, rudder and conbined fin-rudder control systems. In addition, self-running model tests in still water are carried out to make sure if the simulation results are in good agreement with the experimental results.
View full abstract
-
Yasuo YOSHIMURA
Article type: Article
Pages
77-84
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
When a ship proceeds to a berth, a captain or a pilot lets the output of main engine reduce or reverse, and brakes the ship's speed. Then, he adjusts the power of side thrusters or tugs. At a ship-design stage, it is very important to evaluate the manoeuvrability in such shallow water and slow forward speed. In the previous report, the prediction of the manoeuvring ship motion with an adequate main-engine power and forward speed has been presented both in deep and shallow water, using MMG's type mathematical model. However, the behaviour of ship as well as the hydrodynamic forces at the slow forward speed are so much complicated that the conventional MMG's mathematical model can not be applied, because sway and yaw motions sometimes become larger than forward speed by the use of side thrusters or tugs. In this report, steady damping forces and moment acting on hull are mainly investigated, conducting a extreamly large side-slipping and turning CMT. Then the new mathematical model eq. (2) is proposed to describe the ship motion in such slow steaming conditions, by means of simplifying a cross-flow model. From the comparison between simulated ship motion and observed one, it is found that the presented mathematical model can be fairly applied to the prediction of the complicated harbour manoeuvres and also single point mooring systems.
View full abstract
-
Norio JINGU
Article type: Article
Pages
85-95
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
It is very economically important for the planner of the submarine pipeline construction to estimate the required days for the construction. In generally speaking offshore constructions as the laying submarine pipeline are strongly affected by the waves. Therefore, it is important for estimating the workability of the submarine pipeline construction to predict the combined behaviors of the pipe laying barge, pipeline and stingers in waves. In this paper, the theoretical predicting method and the model test conducted verify such predicting method are shown. The predicting method, described in this paper, is the finite element method and directly solves the equation of motions in frequency domain. The predicted results were compared with that from experiments. Consequently, it is verified that the accuracy of the prediction method shown in this paper can be practicaly satisfied. As the first report, in this paper, the behaviors under forced oscillation test and test in waves are described.
View full abstract
-
Mitsumasa IWATA, Kinichi NAGAI
Article type: Article
Pages
97-102
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The cathodic protection is an effective anticorrosion technique for marine structures blow the water line. Therefore, it is important that the potential distributions around structures are made clear in process of structural design. In conventional methods for numerical analysis of the potential distribution in a corrosion cell, the iterative technique has been applied. In this report, a more convenient numerical method to analyse the potential distribution under the cathodic protection is proposed for the purpose of a rational anticorrosion design. In this method, the potential distribution can be obtained by the application of BEM without iterative tecnique, on the assumption that polarisation characteristics of electrodes in eletrolyte are linear.
View full abstract
-
Junkichi YAGI, Yasumitsu TOMITA, Kiyoshi HASHIMOTO
Article type: Article
Pages
103-111
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Many stractural members and mechanical components are generally subjected to variable-amplitude random-sequence loading, or so-called service loadings. At present, in order to predict their fatigue strength, the most reliable method is considered to be random loading fatigue tests simulating real service loadings. In such a case, it is important to examine the statistical characteristics of fatigue life, stress-strain relations under random loading conditions, and so on. In this paper, the following experimental programs were carried out in order to study the above items. The materials used were mild steel and aluminum alloy A5083P-0. Both constant and random loading fatigue tests were performed under load-controlled, axial, fully reversed conditions. The frequency distribution of stress amplitudes was chosen to be exponential. The probability distribution and scatter band of both fatigue life and cumulative damage sum were studied. For aluminum alloy, the life range was approximately 3×10^4 cycles and 5×10^5 cycles; for mild steel, 3×10^4 cycles and 10^6 cycles. About 30 plain specimens were tested for each life range. From these tests the following results were obtained. (1) It was found that the probability distribution of fatigue life for all the above test conditions conformed approximately to normal or logarithmic normal distribution. This was found by both plotting the results on the probability paper and by the x^2 test. (2) Using the F test, it was shown that, for aluminum alloy, the scatter band of fatigue life for random loading was nearly equal to that of constant loading, while for mild steel, it was considerably narrower. (3) It was also shown that the scatter band of fatigue life for aluminum alloy was a little wider than that of mild steel, under both constant and random loading conditions. (4) The probability distribution of cumulative damage sum can be expressed as a normal distribution. (5) Stress-strain relations during random loading cycles are considerably different than those during constant loading.
View full abstract
-
Ken-ichi KITAMURA, Yoichiro OKAMURA, Hiroo OKADA
Article type: Article
Pages
113-120
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In this paper, to investigate the effect of plasticity strain rate on low-cycle impact fatigue bchaviour, tests are carried out on three kinds of steel i.e., SS41, S25C and S45C under repeated impact tensile loads. And effect of the specimen size on impact fatigue behaviour is also investigated. From experimental results, the conclusions are summarized as follows: (1) The process of fracture of the three kinds of materials is creep type and cyclic behaviour of permanent strain ε is almost similar to ordinary low-cycle fatigue behaviour. Its process is divided into three stages which are initial creep stage, constant creep strain rate (Δε_c=dε/dN) stage and accelerative creep stage. (2) The constant creep strain rate Δε_c in the 2nd stage occupying most of fatigue life is nearly equal to plasticity strain measured from the relation between stress and strain. The duration of plastic deformation is also same to the duration of maximum stress T^^-. Therefore, the relation between plasticity strain rate Δε_c and Δε_c is given by Δε_c=Δε_c/T^^- (a) where T^^- is the duration of maximum stress. (3) The relation between Δε_c and impact tensile stree σ^^- is expressed by σ^^-/σ_B=S(Δε_c/ε_f)^β (b) where σ_B is ultimate strength of the material,ε_f is ε at the time of fracture under static tensile test and β and S are experimental constants. (4) The relation between Δε_c and impact fatigue life N_f is expressed by (Δε_c/ E_f)N^m'_f=C' (c) where m' and C' are material constants. (5) The relation between N_f and the beginning life of the accelerative creep stage N_<us> is given by N_<us>=A・N^l_f (d) where l and A are experimental constants. (6) From above results considering the plasticity strain rate, the relation between the low-cycle impact tensile fatigue strength σ^^- and cumulative duration of maximum stress (N_f・T^^-) is approximately expressed by σ^^-(N_f・T^^-)^n'=D' where n' and D' are experimental constants. (7) Through impact fatigue tests for the S25C steel specimens whose lengths are systematically changed, it is found that the effect of the specimen lengths on impact fatigue behaviour is negligible.
View full abstract
-
Apostolos PAPANIKOLAOU
Article type: Article
Pages
121-133
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A quasi third-order potential theory for two-dimensional arbitrarily shaped cylinders in forced oscillation on the free-surface of a fluid is presented. The imposed forced motion is assumed simple harmonic in frequency and the amplitude of oscillation is small but finite compared with a characteristic geometric dimension of the cylinder. A regular perturbation expansion in terms of small parameters to the third-order and Green's Function Integral-Equation Method has been employed to solve the resulting set of BVP's in the course to the third-order. Special attention has been paid to the evaluation of the quasi-third-order velocity potential, oscillating with simple frequency, but being of third-order with respect to the perturbation parameter. The corresponding BVP requires a split of the free-surface inhomogeneity into a slowly decaying and an oscillatory part, ensuring so well-posed BVP's for the contributing velocity potentials to the quasi third order.
View full abstract
-
[in Japanese]
Article type: Article
Pages
135-140
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
[in Japanese]
Article type: Article
Pages
141-146
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
[in Japanese]
Article type: Article
Pages
147-154
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
[in Japanese]
Article type: Article
Pages
155-160
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
App1-
Published: September 25, 1988
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
