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Article type: Cover
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Cover1-
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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Article type: Appendix
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App1-
Published: September 25, 1999
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Article type: Index
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Toc1-
Published: September 25, 1999
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Article type: Index
Pages
Toc2-
Published: September 25, 1999
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Hironori KIKUCHI, Noriyuki SASAKI, Kyouji MURAKAMI, Hajime KIHARA, Kaz ...
Article type: Article
Pages
1-8
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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The characteristics of surface piercing propeller (SSPA, picth ratios, 1.6, 1.3 and 1.0) with shaft horizontally raked are investigated experimentally. The directions of lift forces on blades of usual submerged propellers do not coincide with the advance direction and there is unavailable rotative flow in the wake. These may cause the reduction of propeller efficiency. The present propeller system is proposed to solve them and the conditions of vanishing angle between the direction of lift force and that of advance are introduced. In the present experiment the exact, thrust force is not measured but only torque and shaft force and the propeller efficiency modified from the measured torque is adopted. The above conditions give effective estimations compared with the experimental results and the present propeller system is shown to be superior in the propeller efficiency.
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Yusuke TAHARA, Yasuo SAITOH, Hiroshi MATSUYAMA, Yoji HIMENO
Article type: Article
Pages
9-17
Published: September 25, 1999
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This paper presents optimization of tanker stern form based on viscous flow information obtained from Computational Fluid Dynamics. In this 2nd report, main focus is placed on minimization of delivered horse power at constant ship speed originally designed, and it is shown that a single objective function proposed in the present study is capable for it. The numerical method is based on extension and modification of the method presented in the 1st report on minimization of viscous resistance, i.e., coupling of Reynolds-averaged Navier-Stokes (RaNS) equation solver and successive quadratic programming. Accuracy of RaNS solver in prediction of near wake field is improved by modification of turbulence model. Constraints considered in the present study are basically same as those used in the lst report, i.e., geometrical requirements of optimized hull for displacement, profile, maximum beam and depth, and stern frame line to secure enough space for engine room. In conclusion, the present method appeared to successfully optimize the given tanker stern form, and the modification trends automatically demonstrated in the present work agree well with those commonly in use in traditional tanker hull form design.
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Naoki NAKATANI, Kentaro YAMAZAKI, Taketoshi OKUNO
Article type: Article
Pages
19-24
Published: September 25, 1999
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In order to evaluate the environmental influence around coastal area, it is very important to develop the mathematical model for the environmental simulation. In the present paper, the ecosystem model in Yura area is developed with influence of river and underground water from woods and residential wastewater. The results of numerical simulation suggests that the load from woods affects very strong quickly to nutrium but not so strong to phytoplankton. It can not be ignored to increase production of the wastewater.
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Yukihiko OKAMOT, Satoshi MASUDA
Article type: Article
Pages
25-30
Published: September 25, 1999
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The longitudinal vortex, which originates at the bilge part of full form ships, usually becomes a major part of viscous resistance. In this paper, the energy saving device, which is developed in order to utilize the hydrodynamic energy of longitudinal vortex, is discussed. At first, the basic experiments using two rectangular hydrofoils have been done in order to ensure the energy saving mechanism of this energy saving device called NKK-VENUS (Vortex Energy Utilizing Surfaces), then energy saving effects of NKK-VENUS were investigated using the three types of model ships by the towing tank tests. In these towing tank tests, NKK-VENUS was also used together with the stator type energy saving device NKK-SURF Bulb. At last, the energy saving effects and the interactions of these two energy saving devices are also discussed. In conclusion, much more energy saving effects can be obtained by combining these two types of energy saving devices.
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Masaki IWASAKI, Kazuo SUZUKI, Hisashi KAI
Article type: Article
Pages
31-38
Published: September 25, 1999
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In the previous report, numerical analyses of free surface flow around a sailing yacht were carried out in upright condition with and without leeway by means of PAFS (Panel method Applied to Free Surface flow) inluding rudder effects. In those results, it was concluded that the free surface flow around the sailing yacht with leeway can be simulated well by PAFS. In the present report, some results of numerical analyses for KIT-34 are given under the condition with heel. Hydrodynamic interactions between the main hull, the fin keel and the rudder are also studied, in which the calculated results of hydrodynamic forces acting on the fin keel or the rudder on the assumption that these appendages are advancing under the free surface independently are compared with the calculated results for these appendages attached to the main hull.
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Tatsuo NISHIKAWA, Yusuke TAHARA, Koji MASAOKA, Yoji HIMEN
Article type: Article
Pages
39-46
Published: September 25, 1999
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An important factor in the design of lifting membrane is the accurate determination of its aerodynamic behavior. Recent studies related to membrane wings or yacht sails have introduced iterative coupling of two numerical approaches, i.e., vortex-lattice method (VLM) and finite-element method (FEM) for analysis of the flow fields and the membrane deflection, respectively. In our previous study, we indicated that VLM is not capable for predicting details of flow including viscous effects and three-dimensional-flow separation, and we presented a numerical approach to predict aeroelastic behavior of lifting membrane in onset viscous flow, where the flow fields are solved by a Reynolds-averaged Navier-Stokes (RaNS) equation method. The fully-elliptic RaNS and continuity equations are solved with a zero-equation turbulence model to provide aerodynamic forces acting on the membrane, and FEM considering large deflection with membrane-finite elements is used for estimating elastic characteristics of the membrane. In this paper, we present some applications of this numerical method. For the accurate determination of its aerodynamic behavior, it is necessary to confirm the several computational conditions in which VLM method could not predict the small differences, and, which are corresponding to the improvement of the sail, i.e., improvements of the sail materials, or, addition of a set of battens.
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Akinori YUMUR
Article type: Article
Pages
47-53
Published: September 25, 1999
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This report deals with wall effect on the trailing vortex shedding angle of a rectangular plate wing with low aspect ratio. The rectangular plate wing moves obliquely in the proximity of a uniform wall. On the basis of Bollay's wing theory, calculation of the shedding angle including wall effect is made by using an image of the plate wing. The integral equation which determines vorticity distribution has also unknown quantity of trailing vortex shedding angle. This equation for the shedding angle can be solved by iterative procedure. It is indicated that the shedding angle increases with decrement of distance from the wall. Caluclated values of the shedding angle are compared with observed results obtained from a flow-visualization technique by means of dye tracer method. The calculated values agree qualitatively with the experimental results. Furthermore, variations of hydrodynamic forces on the plate wing with change of the shedding angle are discussed through the results of calculation and experiments.
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Kazuyoshi MAEKAWA, Chikashi SHUTO, Keiichi KARASUN, Kouji NONAKA
Article type: Article
Pages
55-61
Published: September 25, 1999
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Added mass coefficients m'_x, m'_y are important factors to evaluate ship maneuvering motion and are required to describe the ideal fluid force element of our component-type mathematical model of hydrodynamic forces in steering motion. This paper presents a method to calculate added mass coefficients m'_x, m'_y of a ship's superstructure by means of CFD, which can carry out oblique towing tests with constant acceleration. The values m'_x, m'_y of two- and three-dimensional bodies are examined by some methods and in good agreement with theoretical values, potential flow calculations and experimental data except those of a superstructure model of well deck vessel because the size of the superstructure model used in experiment is too small to measure hydrodynamic forces. The results presented in this paper indicate that the CFD method is available to predict added mass coefficients.
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Seiya YAMASHITA, Masahiro ITABASHI, Tatsuo KABAYA
Article type: Article
Pages
63-70
Published: September 25, 1999
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In this paper several aspects of roll stabilization of a floating body in beam waves will be discussed. The equations of rolling motion including coupling effects with swaying motion are given, in which wave-exciting moment is represented by effective wave-slope coefficients (γ). The diagrams to evaluate the γ coefficients readily, are presented for box-shaped floating bodies. According to the diagram, it might be possible to make the γ coefficients zero at any desired wave frequency, by adjusting the position of the center of gravity of floating bodies. Numerica1 computations of rolling motion for the box-shaped floating body with the adapted center of gravity, shows significant reduction of rolling motion. Subsequently, new design consideration for Anti-Rolling Tank (A.R.T.) by using the present equations of motion are proposed. It is also shown .A.R.T. is a practicable device for roll stabilization of box-shaped floating bodies with shallow draft.
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Shin-ichirou TAJIMA, Yoshiho IKEDA, Toru KATAYAMA, Hideaki OKUMURA
Article type: Article
Pages
71-76
Published: September 25, 1999
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In the present study, six-component hydrodynamic forces acting on the 1/4 scale model of a planing craft by planar motion mechanism test at high advanced speed are measured for various planar motions and running attitudes, rise and trim angle. The measured data show that the first order components with the same frequency as that of forced motion are significantly larger than high order comjconents. This means that the hydrodynamic forces model can be expressed by only the first order components of motion's velocity and acceleration. The effect of running attitudes on the hydrodynamic coefficients is significant and it is necessary for maneuverability of planing craft to take into account this effect.
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Yosuke SHIRAKURA, Katsuji TANIZAWA, Shigeru NAITO
Article type: Article
Pages
77-82
Published: September 25, 1999
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The accurate prediction of wave-induced motions of floating structures and hydrodynamic forces acting on their hull are one of the main concerns in ocean engineering. Three types of model with different forms above water are used in this study. The simulated results of motions show that the above water hull forms effect on roll response even in small amplitude incident waves whose frequency is near resonance one. To simulate floating body motion in real ocean, a generation method of irregular waves is confirmed. By using it, we simulated motion of floating bodies in irregular waves for long time.
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Norio YUDA
Article type: Article
Pages
83-91
Published: September 25, 1999
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Recent years, we have a great deal of ships that have VecTwin Rudder. VecTwin Rudder is provided by two rudders that can rotate in a 360-degree arc. The Rudder has eleven typical operation modes, 'Ahead, Hovering, Astern, Turn to Starboard or Port, Astern to Starboard or Port, Rotate to Starboard or Port, and Stern to Starboard or Port'. The operation modes can be done by keeping propeller rotating ahead. The Rudder is very convenient system for use, but the relation between the operation modes and a position of a ship's helm has not been known in detail. The hydrodynamic forces acting on the rudder are important to be understood in order to navigate VecTwin Ship safely. In this paper the author tries to calculate the hydrodynamic forces acting on the rudder in the large angle of incidence by vortex shedding method. The calculation results are reasonably compared with experimental ones, and demonstrate that the combination of larger inner and smaller outer rudder angle, that practically used, is more effective than the opposite combination for both turning and rotating operation modes.
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Sunil MUKHERJEE, Shigehiro HAYASHI, Yasumitsu TOMITA
Article type: Article
Pages
93-99
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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Generally slots are cut into the transverse webs for the passage of secondary members (longitudinal) in ship structures. The present structural design of the slot part makes it too complex and at times strengthened above the required safety levels of hull structure. A zoom analysis of the global model can be carried out to find the possibility of simple slot structure design. This study is a structural analysis of a typical Bulk Carrier by FEM zoomed to the slot part under two selected loading conditions. The rigidity of the longitudinal and the importance of collar plate and web stiffeners are analyzed with different scantlings. Then the shape of slots and its effect on the stress distribution around this particular region are used to find out the possibility of a slot design without collar plates and web stiffeners.
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Kouhei MATSUMT, Toshimasa SAITOH, Hiroshi TANO
Article type: Article
Pages
101-107
Published: September 25, 1999
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In vibration check design for fore and aft vibration of superstructure, it is an important technology to estimate accurate natural frequency and to avoid it from critical resonant region of blade or cylinder frequency when it falls into resonant region unfortunately. In this paper, authors represent a practical design method to change natural frequency of superstructure. Mass-spring system of multi-degree of freedom with rotational spring at base of superstructure is adopted as an analytical model of superstructure. Unknown quantities required to calculation can be estimated, if necessary, by database made up of actual ship data. Most effective structural member and place can be found out from calculated figures of strain energy or kinematic energy distributions obtained for fundamental mode shape. Design values necessary to structural improvement are given by sensitivity relations between design parameter and natural frequency. Optimum design to avoid critical resonant region can be attained successively by this procedure.
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Takayuki UEKI, Masaharu TANAKA, Takashi TSUBOGO, Koji MASAOKA, Hiroo K ...
Article type: Article
Pages
109-115
Published: September 25, 1999
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This paper deals with the basic study on effects of the compressive load on the dynamic behavior of linear floating structures supported by columns such as a kind of floating bridges. At first, a simplified estimation method is presented for the dynamic response of the structure subjected to the longitudinal compressive load and wave induced loads. Next, in order to investigate the applicability of the method, experimental studies are carried out for a basic model which is composed of vinyl chloride strips supported by circular columns. Finally, characteristics of the instability of the liner floating structure subjected to the periodic longitudinal compression are also theoretically investigated for the above basic model.
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Hao LIU, Takashi TSUBOGO, Koji MASAKA, Hiroo OKADA
Article type: Article
Pages
117-125
Published: September 25, 1999
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Eigen frequencies for vertical vibration of very large and comparatively flexible floating structure exist continuously in relatively high frequency zone due to the buoyancy effect. On the other hand, the lowest eigen frequency for horizontal vibration may appear in the lower frequency zone than the heave-mode frequency, because of no effect of buoyancy on the horizontal deflection behavior. Therefore it is important to investigate the dynamic response in the lower frequency zone than the heave-mode frequency. This paper deals with the dynamic behavior for the horizontal deflection of a very large floating structure using the combined model considering the shear rigidity of the main structure and mooring effects. Effects of mooring characteristics and structure parameters on the dynamic response are discussed.
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Koji MASAKA, Noriyasu YOSHIOKA, Hiroo OKADA, Yukio UEDA
Article type: Article
Pages
127-133
Published: September 25, 1999
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In order to examine the strength of stiffened plate structures, it is important to determine an analyzed region as a local structure. In this paper, to evaluate ultimate strength and post ultimate behavior of ship stiffened plate structures, finite element method is used considering elasto-plastic large deflection effects. Collapse mechanisms of stiffened structures are mainly classified into two collapse modes. One is overall buckling mode which means collapse of both stiffeners and panels. And another is local buckling mode which means collapse of panels or stifeners locally. To analyze these modes and their interactions, analyzed region is decided in this study. Satisfying the boundarycontinuity between adjacent structures under combined loads, Multi-freedom Dependent Constraint]VIethod is applied for boundary condition.
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Masakazu SHIBAHARA, Hisashi SERIZAWA, Hidekazu MURAKAWA
Article type: Article
Pages
135-144
Published: September 25, 1999
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Based on the interface element proposed for the crack propagation problems, a finite element method (FEM) using temperature dependent interface element is developed. The proposed method is applied to the analysis of occurrence and propagation of hot cracking in welding. Especially the hot cracking extending from the starting end of the narrow rectangular plate under bead welding is examined using the proposed method. The following conclusions are drawn. In case of high welding speed, large heat input and small width of plate, hot cracking is likely to occur. This agrees with the phenomena generally observed in experiments. The proposed method can simulate not only occurrence and propagation of hot cracking, but also the contact of the starting edge of the plate after complete cooling.
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Zhengqi WU, Hisashi SERIZAWA, Hidekazu MURAKAWA
Article type: Article
Pages
145-153
Published: September 25, 1999
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Based on the interface element proposed in the first report, a computational method for the analysis of dynamic crack propagation is developed by introducing the effect of inertia force. The proposed method is applied to the dynamic crack propagation in prestressed elastic plate with a center-crack and the analysis of Charpy impact test. In case of the elastic plate, it is numerically shown that the crack propagation speed increases with the prestress and it converges to the Rayleigh's wave speed. It is also shown that the crack propagation speed is determined only by the surface energy and independent on the bonding strength. Through the simulation of Charpy test, it is found that the strength increases but both the ductility and the absorbed energy decrease when the yield stress becomes large.
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Yasumitsu TOMITA, Kiyoshi HASHIMT, Naoki OSAWA, Junji SAWAMURA, Nobuta ...
Article type: Article
Pages
155-161
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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The aim of this study is to clarify the heat transfer from combustion flow field to plate surface during line-heating process. 3-dimensional computer code for the caluclation of combustion flow field is developed by taking into consideration of radiation heat transfer. Impinging turblent gas jet flames are numerically analyzed. In consequence, the flame structures formed near the jet nozzle such as under-expanded jet flames, corn flames at jet nozzle and the increase of both velocity and temperature of combustion are shown. And influence of the radiation heat transfer in the flow field is made clear.
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Kenji OKIMOTO, Yoji HIMENO, Yusuke TAHARA
Article type: Article
Pages
163-171
Published: September 25, 1999
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In the previous paper, the authors proposed a new k-e model and improved prediction accuracy of the mean flow field with longitudinal vortex. But in the high vorticity region, it was difficult to express normal Reynolds stresses accurately in view of Boussinesq assumption. To improve this problem, the authors examined the nonlinear eddy viscosity expression and combined the author's k-E model with it. The fully-elliptic Reynolds-averaged Navier-Stokes (RaNS) and continuity equations are solved with a nonlinear eddy-viscosity turbulence model, where k and E are solved using two-layer technique. Discussions are made concerning the validity of the nonlinear k-E model through the comparison between the computational results and experiments.
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Satowa NISHIMURA, Yoshiho IKEDA
Article type: Article
Pages
173-182
Published: September 25, 1999
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Recently transportation services of passengers and cars by fast car-ferries over 40 knots have been rapidly developed in the world. In this paper a new general cost model including factors of comfort, riding comfort, convenience, exhaustion and safety as well as fare and traveling time is proposed to predict the share of fast car-ferries in total demand of passengers between two places. Using the model and a cost analysis for operation, the competitiveness of fast car-ferries can be evaluated with other transportation system. As a case study the feasibility study on a fast car-ferry service between Osaka and Tokushima is carried out to find that fast car-ferries can obtain a share of 40-50% in total demands of passenger between the cities and that the service would be promising.
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Nobuhiro BABA, Eigo FUKAI, Yasunori SAKAGUCHI
Article type: Article
Pages
183-188
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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Gravity currents on slopes are studied by numerical experiments based on the finite volume solution of the Navier-Stokes equation. The head of the gravity current increases in volume, and the roll up of the interface and the mixing across it become violent with the slope. For steep slopes the enlarged head is divided from the subsequent current, the isolated head advances forward and accelerates to be divided again. The front is subject to the acceleration and deceleration repeatedly, but the acceleration effect of the gravity along the slope does not clearly appear in the fluctuated speed of the current front because the deceleration effect due to the enlargement of the head compensates for it. The average front speed increases with the angle of the slope in a range from zero, and reaches to the maximum speed at a certain angles of slope. At larger angle, the front speed decreases with the angles, which is caused by the division of the head and the violent mixing. It is elucidated that this variation of the front speed is associated with the change of the inner structure of the head from the parallel flow to the normal flow to the slope.
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Yasunori SAKAGUCHI, Nobuhiro BABA
Article type: Article
Pages
189-194
Published: September 25, 1999
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Interaction of gravity currents with head and tail ambient flows is investigated by computation using the adaptive grids moving with the head of the current. The incompressible Navier-Stokes equation for an inhomogeneous fluid, the continuity equation and the transport equation of the relative variation of density are discretized by the finite volume method. The use of the moving grid system raises the computational efficiency as well as the resolution of the moving head. The ambient flow is incorporated with the implementation of the inflow and outflow boundary conditions. The results indicate that the front speed relative to the ambient flow varies in a nonlinear fashion when the boundary layer develops along the wall. The tail wind makes the head round and thicker and hence it reduces the speed of the head. On the other hand, the head wind makes the head sharp, thinner, and longer, and then the stable interface suppresses the mixing across the density interface. It is found that the boundary layer along the wall affects the inner structure of the current head according to the ambient flows.
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Nobuhiro BABA, Norikazu GODA, Kenichi KITAURA, Futoshi MASUDA
Article type: Article
Pages
195-201
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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The three-dimensional flow structure around a circular cylinder is investigated by visualization experiment using aluminium flakes as tracers when it impulsively starts to rotate at a constant speed in the range of the Reynolds number, 500 <__- Re <__- 4000. The flow in the boundary layer along the cylinder surface with the thickness larger than the critical value is subject to the three-dimensional instability, and then it forms streamwise vortices around the cylinder. The flow structure in the early stage is a raw of these streamwise vortices of almost same size and of opposite rotations alternately along the cylinder axis and it is extended to the whole depth of the boundary layer. Among these vortices adjacent ones interact with each other so as to coalesce or absorb another repeatedly at times and places, and consequently the vortices become greater in size and fewer in number. The boundary layer develops along the cylinder surface with the thickness increasing with time to the power of order 1/2, while the flow structure of streamwise vortices with time to the power of order 1. The development of the former boundary layer is scaled with viscous unit, while that of the latter structure depends on the outer scales as well. In addition the number of vortices decreases exponentially through the interaction with each other. At the higher Reynolds numbers, the local interaction much stronger, but not synchronously in the azimuthal direction, causes to break the axisymmetry of the flow.
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Kentaroh KOKUBUN, Shoichi HARA, Kenji YAMAKAWA, Masami IWAI
Article type: Article
Pages
203-210
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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Towing problems of a box-shaped unit of the huge floating structure are studied experimentally by towing an unit model. The effects on the towing tension, bending moment and motion are investigated by varying the wavelength, the towing speed, and the draft of the unit model. The experimental transfer functions of the wave bending moment and the vertical displacement are compared with those from the numerical calculations based on the pressure distribution method. The experimental transfer function of the surge motion is compared with the theoretical calculations based on the strip theory. The added towing resistance in waves is also investigated by comparing the experimental results with the numerical results. Moreover, the reduction of towing resistance is proved by attaching either cut-up type or forward-plate type appendage in front of the unit model. The reduction of towing resistance is supposed to be more effective on the full-scale unit; than on the model unit.
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Toshio SUZUKI, Hirokazu YAGINUMA, Teruhisa OGATA
Article type: Article
Pages
211-218
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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Remote-sensing technology is very useful for observation of a vast surface of ocean in real time, and it has been utilized widely. In this paper, the method of measurement for the significant wave height and the mean wave period in irregular waves using a continuous microwave from the satellite has been investigated by computer simulation. The spectrum of received radar signal has been analyzed. Obtained distribution of wave height and wave length show good agreement with that of simulated wave well.
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Kazuhiko HASEGAWA, Hideki HAMAMOTO, Kho Shahriar IQBAL
Article type: Article
Pages
219-225
Published: September 25, 1999
Released on J-STAGE: April 01, 2018
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To achieve a sustainable development to the environment the scope of modal shift from truck to ship is discussed. Considering some environmental impacts, the environmental effects conducted by truck and ship for an assumed model case are calculated and compared. The calculations are carried out for four different scenarios. The superiority of marine transports over road vehicles from ecological viewpoint is shown by environmental index estimated using life cycle impact assessment.
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Article type: Appendix
Pages
App2-
Published: September 25, 1999
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Article type: Bibliography
Pages
Misc1-
Published: September 25, 1999
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Article type: Appendix
Pages
App3-
Published: September 25, 1999
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Article type: Cover
Pages
Cover2-
Published: September 25, 1999
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