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Article type: Cover
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Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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Article type: Appendix
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Published: March 25, 1999
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Article type: Index
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Published: March 25, 1999
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Article type: Index
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Published: March 25, 1999
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Isao FUNENO, Kazuo NOZAWA
Article type: Article
Pages
1-6
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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It is necessary to design a low noise propeller for oceanographic research ships and military ships. In order to reduce tip vortex cavitation, which is main source of propeller underwater noise, it is important to estimate the inception of the cavitation as accurately as possible. Since the cavitation-causing tip vortex is susceptible to viscosity strongly, the method of the estimation with high accuracy is not established. In this paper, the authors describe an analytical method of flow around a propeller as a first step. The paper presents computation results of the flow around a highly skewed propeller, which is a typical form of low noise propeller, and verification by comparison with the experimental data on public view. Furthermore, the paper presents an application to the evaluation of propeller noise level using the computed flow data.
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Dian J. GEORGIEV, Mitsuhisa IKEHATA
Article type: Article
Pages
7-19
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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The performance of screw propellers in unsteady flow and the stress distribution and deflection of their blades are computed by surface panel method in combination with the thick shell finite element method, and compared with the experimental results. The characteristics of the surface flows on rigid and deflected blades are approximated by Taylor's series expansion and minimization of the kinetic energy of perturbation velocities. A new method also is applied to estimate the time derivatives of the perturbation potential on the basis of a minimization of the change of its kinetic energy. The comparison between calculated and measured data for pressure distribution confirms the reliability of the estimation of unsteady characteristics at tip of the propeller.
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Yumin SU, Mitsuhisa IKEHATA
Article type: Article
Pages
21-28
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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In this paper, a numerical method for the design of marine propellers is described. The lifting-line model discretized with the vortex lattices and the variational calculus are used to determine the optimum circulation of the propeller blades under the design requirement. According to this optimum circulation distribution, the specified type of pressure distribution on the propeller blade and the thickness of the blade section, the blade of propeller is designed by a numerical design method based on the sueface panel method. By Morino's surface panel method the performance of the designed propeller is analysed and the pitch of the designed propeller is modified to make its circulation distribution be consistent with the optimum circulation distribution. The propeller in the uniform flow and the wake adapted propeller in the circumferentially uniform flow are designed as examples.
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Yusuke TAHARA, Yasuo SAITOH, Yoji HIMENO
Article type: Article
Pages
29-36
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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This paper presents optimization of tanker stern form based on viscous flow information obtained from Computational Fluid Dynamics. The numerical method is based on coupling of Reynolds-averaged Navier-Stokes equation solver and nonlinear programming technique, i.e., finite-analytic discretization and PISO-type velocity/pressure coupling method, and successive quadratic programming, respectively. In this lst report, minimization of viscous resistance is considered and stern form of a given tanker hull is optimized with inequality constrains such that displacement of the modified hull is equal or larger than that of the original, and the profile and maximum beam length as well as depth of the modified hull are same as those of the original. In the following, overview of the present numerical method is described and results are presented for optimization of SR221b tanker hull, including discussion of identification or salient differences of geometries and flows between the original and optimized hull forms. In addition, trends of modification of the stern form are evaluated by a viewpoint of tanker-hull-form designer. In conclusion, the present method appeared to successfully optimize the given tanker stern form, and a good agreement is demonstrated between trends displayed in the present modification and those commonly in use in actual tanker hull form design.
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Tokihiro KATSUI, Kiyoshige MATSUMURA
Article type: Article
Pages
37-47
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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An adjoint variational principle for determination the wetted surface of planing ship considering gravitational effect is proposed based on a principle regardless of gravitational effect. A method of high aspect ratio approximation is investigated. A simple relation is obtained between the Froude number based on the wetted length in running condition and the one based on the still water length. The solution of wetted surface of planning plate agreed with experimental results, compared with the case regardless of gravitational effect.
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Abdul MUNIF
Article type: Article
Pages
49-55
Published: March 25, 1999
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This paper discusses a new approach for prediction the occurrence of broaching-to phenomenon in astern seas, Since there is no a standard test of broaching-to up to the moment, here, a zigzag test is used to predict such phenomenon. By means of this test several causes, which were identified by previous researchers, lead to broaching can be easily seen. Several zigzag simulations were carried out to obtain critical lines of broaching. Finally, a comparison between the simulations and the experimental results from free running test using auto pilot system is described, the comparison shows a good agreement
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Yoshiho IKEDA, Hideaki OKUMURA, Jiro NIINA, Toru KATAYAMA
Article type: Article
Pages
57-64
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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Very limited numbers of studies on maneuverability of hard-chine planing hulls have been carried out, and any theoretical or experimental procedures to simulate the maneuvering characteristics of them have not been established yet. Although the most important characteristic that is different from that of a conventional displacement vessel seems to be the significant effects of changing of running attitude on maneuvering, measured hydrodynamic forces to use in a motion equations for maneuverability of six-degree-of-freedom for them are almost nonexistent as far as the authors know. In order to clarify the effects, a six components of hydrodynamic forces acting on the scale model of a planing craft in oblique towing condition are measured using a high-speed carriage, maximum speed of which is 15m/s, in the towing tank of Osaka Prefecture University. The model is fully captured by a six-component load cell, and its attitudes, trim, rise and heel angle, are systematically changed. The experimental results show that the hydrodynamic forces are proportional to the square of advanced speed at planing speed, and demonstrate that the effects of attitude on the hydrodynamic forces are significant. The dependency of each hydrodynamic component on the running attitude are identified on the basis of the experimental results
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Dong Yeon LEE, Mun Keun HA, Hyun Jo KIM
Article type: Article
Pages
65-73
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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Recently various types of special vessel as like FPSO, shuttle tanker, and drill ship come to fore and are ordered from the European ship owner, because of the necessity of multi-purpose vessel and deep sea drilling rig. Traditionally mooring systems of offshore structures has been used to keep her position in relatively shallow water but nowadays Dynamic Positioning System is being used to keep her position in deep sea. In this study, DP simulation program is introduced. The program can predict the time varying motion of the ship with mooring and DP propulsion system in the horizontal plane. Motion equations used in this program considers the wind, waves, and current as the external forces and mooring line forces in addition to propulsion systems. To find the input variables of the positioning systems, PID and LQR processes are considered as the control system. Furthermore Kalman filter and digital filter are used to exclude the noise and high frequency components of motions in the calculation of input power. For the validation of this program, model test results of 125K shuttle tanker and 103K drill ship are used. The comparison between model tests results and sinulation results showed good agreements.
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Shigeru NAITO, Munehiko MINOURA, Haruaki SAKASHITA, Kenta TANAKA
Article type: Article
Pages
75-82
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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When experiments are made in waves, a problem of the reflected waves at the basin wall is very serious. In order to avoid this problem an absorbing wave maker is necessary to be equipped, which has the performance to generate and absorb waves simultaneously. We designed fifty element absorbing wave makers controlled by the micro computer based on our theory, and investigated the configuration of a wave making basin with these absorbing wave makers around the whole of the basin. Using them, we can set up a wave basin having an arbitrary configuration such as circle and ellipse etc. We compared a wave elevation between the experimental results and theoretical ones in the wave making basins with such as configurations.
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Kouhei MATSUMOTO, Toshimasa SAITOH
Article type: Article
Pages
83-89
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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Database method proposed by authors in the previous paper were applied for vibration response problems of a fore-and-aft vibration of superstructure. As an object of investigation, Accelerance (Acceleration per unit exciting force at peak frequency) at Navigation bridge deck was selected to remove difficulty and uncertainty of estimation for an exciting forces. General method to construct Database from vibration test results of existing ships was described. Various variables concerning to vibration characteristics of superstructure and ship hull were examined as an expression of empirical formula by regression analysis. It was found that √^3<l_m/H> and l_m/H^2 (l_m=mean side wall length, H=height excepting poop deck) indicate comparably better factor to regression line of Accelerance of superstructure.
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Yasumitsu TOMITA, Kiyoshi HASHIMOTO, Naoki OSAWA, Nobuyuki YAMAGA, Kat ...
Article type: Article
Pages
91-99
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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A 2-dimensional plane strain crystalline FEM code which takes into account 3-dimensioanl crystalline slip is developed. The cyclic deformation behavior of the center section of a f.c.c. rectangular parallelepiped single crystal is calculated by using this developed 2-dimentional code and the 3-dimentional code developed in the previous report. The properties of plastic strain localization and irreversible slip generation in the course of loading history of these two cases are quite different from each other under the conditions calculated in this report. Therefore, 2-dimensional plane strain analysis is inappropriate for the analysis of fatigue crack initiation process in some cases.
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Akira KONDO, Katsuhito YAMAGUCHI, Eiichi NISHIKAWA, Tatsuki HARA, Ryuj ...
Article type: Article
Pages
101-109
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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Marine traffic in Osaka bay is very intensified and much emission amounts of SO_x and NO_x from ships is released but there is no regulation about atmospheric pollutants emission from ships. In this paper, we investigate the emission amounts of SO_x, NO_x and HC from vehicle, factory and ships in Osaka bay area and estimate the influence of ship emission on the atmospheric pollutants concentration, using the mesoscale model to predict the wind fields and the concentration prediction model including the dry deposition and photochemical reaction model. In Osaka bay area, the emission amounts of SO_x and NO_x from ships were about 30% of the total emission amounts, respectively. Using these emission data, the atmospheric pollutants concentrations were simulated on a summer fine day when high oxidant concentrations were measured at several observatories and were compared with observed data. Though some differences were seen between the simulated and observed values, the diurnal variation agreed reasonably. Next, the numerical simulation was carried out except for ship emission amounts and estimated the influence of ship emission on the atmospheric pollutants concentrations. It was found that ship emission raised SO_2, NO_2 and NO concentration not only in shore area but also in 40km inland.
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Toshimasa SAITO, Tomoko KITANO, Osamu SONODA, Teruaki MAEDA, Toshimits ...
Article type: Article
Pages
111-117
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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The work in an ocean oil field is very dangerous and there are many accidents. So there are demands for taking suitable measures against the hazards. Deflagration of inflammable crude oil gas is one of the major accidents. There are many studies and experiments regarding deflagration for gas-air mixtures on a small scale. But, there are only a few cases studied on a large scale, and the phenomenon is not clear enough. This paper presents a pressure calculation method when deflagration occurs in a mud treatment room in a semi-submersible drilling rig for the development of useful calculation tool for basic design.
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Nobuhiro BABA, Yasunori SAKAGUCHI, Satomi ITO
Article type: Article
Pages
119-127
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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The effect of a vertical barrier on the behaviour of a gravity current in an open channel was investigated in the experiment and the computation. The unsteady density field during the interaction of the current with the barrier was measured by the digital image processing. The measurement system uses the property of the light transmitted through coloured water and absorbed at the increasing rate with the dye concentration. The digital images of the coloured water in two-dimensional motion taken with a digital video camera on the side of the tank were directly sent to the computer to convert the brightness to the concentration and to the density on every pixel in the frames. The computation was also performed in the same condition as the experiment to compare their results. The incompressible Navier-Stokes equation for an inhomogeneous fluid together with the transport equation for solute was solved by the finite volume method developed in the previous paper and modified in this paper to obtain a stable solution of the flow beyond the barrier. The results reveal the inner structure of the head of the current on impact. The heavy fluid runs up the vertical wall at the almost same speed as the advancing speed of the horizontal current on the bottom before the collision. The raised heavy fluid falls down along the wall so as to generate a solitary wave propagating back through the stratified layer left by the original current. The height to which the current runs up the wall and the time during which the elevation of the interface lasts are both affected by the traveled distance as well as the initial depth of the current, which indicates that the regime of the development of the current is one of the important factors that determine the behavior of the current meeting a barrier.
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Nobuhiro BABA, Takayuki KASHIMA, Eigo FUKAI
Article type: Article
Pages
129-134
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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The numerical model of mixing in stratified flows developed in the previous paper was extended to the unstable condition of the mixing by surface cooling. The use of the relative variation of density to the initial density difference as one of principle variables accures accurate representation of small variation of density due to temperature change. The transport equation of this quantity together with the incompressible Navier-Stokes equation for an inhomogeneous fluid is solved by the finite volume method. The surface cooling with the constant temperature on the top is modeled as the Dirichlet boundary condition for the transport equation. The two-dimensional computation was carried out to examine the mixing process in an infinitely large area of temperature stratification by surface cooling. Vertical profile of horizontally averaged temperature shows the interface separating the mixed layer from the stratified region. It is confirmed that the rate at which the interface descends depends upon the ratio of the temperature difference due to the surface cooling to that due to the stratification. The roll structure extended to the whole depth of the mixed layer is found to be fundamental to the mixing process in the two-dimensional flow. At an early stage the structure consists of a row of rolls with opposite rotation alternately aligned with the top surface and it is still maintained even in the following chaotic circumstance of the growth and merging of rolls where some distinct blobs penetrate the mixed layer.
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Koji OTSUKA, Naoki NAKATAMI, Masayuki MIYACHI, Mineo FUJIWARA, Takashi ...
Article type: Article
Pages
135-144
Published: March 25, 1999
Released on J-STAGE: April 01, 2018
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The purpose of this study is to clarify the water purification mechanism of artificial lagoon using an ecosystem modelling technique. In the third report, an ecosystem model for an artificial lagoon in Rinku Park was developed with reference to the results of field investigations. The results of the numerical simulation suggested that the nutrient fixing effect of seaweed is large, and water soil qualities significantly depend on the biological parameters about seaweed and sessile animals. Some numerical experiments using the developed ecosystem model were also performed.
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Article type: Appendix
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Published: March 25, 1999
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Article type: Cover
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Published: March 25, 1999
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