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Article type: Cover
Pages
Cover1-
Published: September 25, 1997
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Article type: Appendix
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App1-
Published: September 25, 1997
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Article type: Index
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Toc1-
Published: September 25, 1997
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Article type: Index
Pages
Toc2-
Published: September 25, 1997
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Frederique LARRARTE, Yoshiaki KODAMA
Article type: Article
Pages
1-6
Published: September 25, 1997
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For energy conservation reasons, viscous drag reduction is of great interest for full scale ships. A lot of references report skin friction or total drag reduction when bubbles are injected into the boundary layer on the hull. As experiments on a full scale ship is almost impossible, the scale effect in the trajectory of bubbles injected at the bottom of a hull was investigated using geosim models. After a description of the experimental work, the numerical scheme used to compute the bubble trajectories is explained. Then the experimental and numerical results are presented and discussed. The influence of the scale effect and of the injection location is shown.
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Yoshiyuki TANAKA, Katsuo SUZUKI
Article type: Article
Pages
7-14
Published: September 25, 1997
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From the viewpoint of obtaining low viscous drag at large Reynolds numbers for axisymmetric bodies over which the boundary layer is fully turbulent, an iteration method is developed for solving the inverse problem of getting body shape from the velocity distribution by means of boundary integral equation for Stokes stream function. A calculation formula, an integral of a power of the potential-flow surface velocity, is used to get the viscous drag. Using an approximate steepest-descent-method in the optimum value problem the minimum drag shaping is conducted. The obtained value of the minimum drag and the body shape is nearly equal to ones known already. The presently obtained know-hows and means are expected to obtain the body shapes over which the boundary layer is partially laminar.
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Yoshiaki TSUKADA, Munehiko HINATSU, Jun HASEGAWA
Article type: Article
Pages
15-20
Published: September 25, 1997
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Although the importance of ship performance in waves has been stressed, only a few set of data of wake measurments are available in which a ship runs in waves. Adding to that, today's CFD techniques have been able to offer flow data around ships. Therefore we will need verification data of the flow field around a ship in the case when the ship runs not only in still water but also in waves. This paper is concerned with the wake measurments of a ship in regular waves. First we verified the wake measurement system by measuring the regular wave field itself and then by oscillating the probe in a still water flow field. The wake measurements were carried out with λ/L=1 and 0.5. In both conditions, the ship was towed in heave and pitch free condition and motion fixed condition. Furthermore a forced pitch conditon in still water was also carried out. Measurement data were presented by showing the change of wake fraction and mean circualtion in one encountering period and we thus showed the relation between the change in the wake and the ship motion and incident waves.
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Satoshi MASUDA, Yoshikazu KASAHARA
Article type: Article
Pages
21-28
Published: September 25, 1997
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The purpose of this paper is the validation of a simulation for viscous flow fields around the ship by using CFD (Computational Fluid Dynamics) code. Recently, in naval architectare many kinds of CFD codes have been developed and have come to be used as simulation tools in the ship design. Using CFD code as a hull design tool, it is most important to understand the difference between real flow and computed results. This paper clearly presents the quantity difference between a measured flow field and a computed one. First this paper validates that CFD code can simulate the Reynolds number effect in towing condition by comparing the computed results with the measured flow. Second the comparison of tow type ships which have same aft body and different fore body represents that the CFD code can simulate the difference of the flow field based on fore body shape. Finally, it is shown that the CFD code can qualitatively simulate the flow in self-propulsion condition without rudder. In these results, CFD code is an effective tools to estimate the flow around the ship.
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Shumei NARITA, Yoshikazu KASAHARA, Kazuyoshi HIROTA, Kunihiko SHIROTA
Article type: Article
Pages
29-35
Published: September 25, 1997
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A Lift & Buoyancy-Supported Craft (LBSC) is a variety of fully submerged type hydrofoil craft. A LBSC is supported by the buoyancy of a submerged body and the dynamic lift generated by the hydrofoil while cruising. This concept was envisaged to create a high speed and exceptional seaworthy craft of much bigger size, higher payload and longer cruising range than pure hydrofoil craft. This paper describes two kinds of model test methods and their results for LBSC in a towing tank, using a model without propulsion device. One is the captive model test to determine the hydrodynamic characteristics of the craft at an equilibrium of the forces and the moments at a steady running condition. This method can be used for studying the hydrodynamic performance of a LBSC or pure hydrofoil craft in calm sea conditions in various modes of operation. The other is a towing test with wire to examine the running attitude during Take-off stage. This method is useful for checking the longitudinal stability of the LBSC at Take-off state.
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Yoshikazu KASAHARA, Shumei NARITA, Satoshi MASUDA, Kazuyoshi HIROTA, K ...
Article type: Article
Pages
37-43
Published: September 25, 1997
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This paper describes the issue of the correlation between predicted and measured resistance characteristics of a Lift & Buoyancy-Supported Craft (LBSC). LBSC is a fully-submerged type hydrofoil craft with a torpedo-shaped submerged body which provides buoyancy to support a considerable portion of the weight of the craft. The experiments at Osaka Bay were carried out by using HAYATE which is a one-sixth scale to the full-size Techno Super Liner. A 1/3.58 scale model of HAYATE was tested in the towing tank to predict HAYATE's resistance characteristics. As for extrapolating model resistance to the ship, a 2-dimensional extrapolation method was adopted, namely the total resistance was divided into frictional resistance and residuary one: the former is the sum of frictional resistance of each hull component. HAYATE's resistance characteristics obtained from the sea trial agreed fairly well with predicted one from the model test. Discussion was made as to the effect of the ship surface irregularities and the paint roughness on the frictional resistance.
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Yutaka MASUYAMA, Masamitu TAKAYAMA, Yoshito TUKAMOTO, Yoshihiko HAKOZA ...
Article type: Article
Pages
45-52
Published: September 25, 1997
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The solar boat project at the Kanazawa Institute of Technology (KIT) has started in 1991 as a student research theme. From 1995, a fully submerged hydrofoil system has been adopted for the solar boat in order to reduce wave making resistance of the hull. A fore foil height-control-system was introduced to adjust pitching motion of the boat and its height from surface of the water. For the main foil, an aileron mechanism had a function to control rolling motion in cruising of the foil-born mode. Several tests were conducted to clearly understand the performance of the solar boat. A testing apparatus for the full-scale propeller was constructed and measured the propeller performance on the sea. Hull resistance with the hydrofoil system was also measured in a towing test on the sea. The boat speed was estimated by using the both data of propeller performance and the hull resistance. The estimated values coincided well with the characteristics of the actual solar boat.
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Takahito TAKAHASHI, Akira KAKUGAWA, Hideki KAWASHIMA, Yoshiaki KODAMA
Article type: Article
Pages
53-58
Published: September 25, 1997
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Skin friction reduction measurements using microbubbles were carried out in a two dimensional channel flow. Microbubbles are expected to reduce the skin friction which occupies a large part of the total ship drag. An adaptation to a real ship is difficult because of the very large amount of microbubbles. In order to adapt to a real ship we must search for more effective bubble conditions which are bubble size, bubble position and bubble scale effects. We measured the local skin friction reduction in a small high-speed water tunnel, systematically changing the main velocity and measurement position from the bubble injection point. At the same time, we measured the diameter of bubbles from the photographs.
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Shigeru NISHIO, Taketoshi OKUNO, Nami HIRATA
Article type: Article
Pages
59-65
Published: September 25, 1997
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Present paper describes the principle of an image measurement of three-dimensional flow field by means of statistical analysis. The technique is based on the fact that the probability of the particle passing is proportional to the flow speed if the particle concentration is uniform and constant through the measurement. In the present study, the measurement technique is extended so as to apply it on the three-dimensional velocity field. The governing equation is formed using the Lagrange's differentiation, and the process is similar to it of the so-called spatio-temporal derivative method. The governing equation is expressed by the vector notations, and it is easy to apply on three-dimensional field. Multi sheet light illumination system which is synchronized to the freezing cycle of images realize the three-dimensional measurement. The principle of the measurement is confirmed by the numerical simulations.
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Tetsuya KITAMURA, Yusuke TAHARA, Youji HIMENO
Article type: Article
Pages
67-78
Published: September 25, 1997
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This paper presents a study on layout optimization problem of tow-dimensional tandem hydrofoils under free surface. Numerical method is based on nonlinear programming approach, where the local linear solution is obtained by affin scaling interior method. Source-circulation panel method is used to compute wave-making resistance, which is minimized in the optimization procedure. The present method is capable for unlimited number of wings; however, in the present paper, results are presented for four-wing problem, i.e., each of fore and aft. wing systems is composed of main wing and Fowler flap, whose relative location and attack angle are used as design parameters. It is shown in the results that the hydrodynamic forces acting on main wing of aft. wing system has the largest influence on lift and drag forces of whole system, and also the initial design parameters must correctly be given in order to obtain non-trivial optimized solution.
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Yusuke TAHARA
Article type: Article
Pages
79-90
Published: September 25, 1997
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This paper presents a numerical approach for steady ship-wave problem, which is based on extension and modification of Dawson-type Rankine-source method in order to utilize arbitrary topology of free-surface panels. The wave radiation condition is numerically given, where 3rd-order upstream differential operator evaluates 2nd-derivative terms in the free-surface boundary condition. In this 1st report, the main emphasis is placed on application of O-type as well as conventional H-type topology free-surface panels. It appears that the former offers advantages over the latter due to the efficient panel distribution and improved resolution of the local-region bow-and shoulder-wave systems. The computational results are presented for Wigley and Series60 C_B=0.6 ship models including detailed comparisons with experimental data.
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Tadao YAMANO, Yasuo SAITO
Article type: Article
Pages
91-100
Published: September 25, 1997
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Estimation of wind forces has become to be often required in ship design, for example, to check manoeubrability in strong wind on ships with large above-water surfaces such as PCC and LNGC, to conduct wind correction to speed trial results, and to estimate sea margin. The authors have tried to develop a practical estimation method of wind forces by which wind force coefficients can be estimated more accurately than ever in a short time using a small number of data which properly represents above-water ship form characteristics and are easily available on any ship. This paper describes the development.
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Shigeru NAITO, Naoaki NISHIMURA
Article type: Article
Pages
101-112
Published: September 25, 1997
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Research on the stress acting on the side longitudinal girder is requested because some fatigue accidents have been reported. This paper shows the research results on the following two problems. 1. Mutual interference effect between the axial force and the lateral force acting on the side longitudinal girder of ships on the stress. 2. Nonlinear effect of pressure acting on the ship side hull portion near the free surface on the stress. On the first problem, the approximated probability density function of the stress can be obtained. As the results, we can discuss the mutual interference of them. On the second one, by using the theoretical mean and variance values of the nonlinear pressure, the quasi-linear stochastic investigation on the nonlinear pressures and loads can be performed. By using these results, the long term prediction of the stress is carried out and is compared with the experimental results of the actual ships. The proposed results agree with the experimental one.
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Michio UENO, Tadashi NIMURA, Toshifumi FUJIWARA, Koji NONAKA
Article type: Article
Pages
113-121
Published: September 25, 1997
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Free running model test using Real-Time-Kinematic On-The Fly (RTK-OTF) mode in GPS was carried out at 80-by-80 meter square ship model basin. The measuring system consists of three GPS receivers, one radio link and an onboard personal computer for data storage. One GPS receiver was located on the shore as a base station which transmits reference data every 1.0 second and two others were on the model ship as mobile stations which produced fore and aft positions data every 0.2 second (5Hz) or 1.0 second (1Hz) selectively. Ultrasonic Positioning System (UPS) was also used for comparison to discuss accuracy and reliability of GPS data. It is concluded that GPS, even in 5Hz fast sampling if it is used in RTK-OTF mode, has sufficient accuracy for positioning and analyzing manoeuvring motion of a free running model ship in calm water and can be a reliable tool not only because of its accuracy but also the property that it is portable, does not require calibration and does not disturb flow around model ships.
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Kohei OHTSU, Jin Seok PARK
Article type: Article
Pages
123-127
Published: September 25, 1997
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One of the authors of this paper has developed the Roll Stabilization with Rudder Control by using Multi-variate Auto-Regressive Model. However, this system, which is of fixed gain type autopilot, has no abilities of being adaptable to the changing ocean conditions and the ship's dynamics. In this paper, this idea has been expanded in order to develop the Batch Adaptive Rudder-Roll Control System. Applying the on-line judgment procedure on a locally stational time series proposed by Ozaki and Tong, a practical adaptive rudder-roll control system can be desigend. The main content of this paper is to investigate the efficiency of the system and design of the Batch Adaptive Rudder-Roll Control System together with the results of experiments of the actual ship.
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Masaru TSUJIMOTO, Shigeru NAITO
Article type: Article
Pages
129-136
Published: September 25, 1997
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In this paper, a new theoretical method to estimate the ship speed in actual seas using probabilistic method is proposed. The speed loss is classified into the following five factors: (1)aging effect, (2)fouling effect, (3)wave effect, (4)wind effect and (5)ocean current effect. These effects are described with probability density functions. As all factors are independent of each other, the convolution integral is available for obtaining the joint probability density function of them. A container liner is selected for the calculation and her service route is Pacific South-West Coast route (PSW). A long term prediction for 10 years is conducted using wind and wave statistics of the route.
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Akinori YUMURO
Article type: Article
Pages
137-142
Published: September 25, 1997
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Some numerical calculations of maneuvering hydrodynamic forces on a ship hull with heel angle are carried out by using Bollay's lifting surface theory. With the assumption of rigid free-surface, the ship body is replaced by a rectangular wing with dihedral angle. Here, the dihedral angle corresponds to heel angle of the ship body. Sources are distributed over the lifting surface to represent thickness effect of ship breadth. The source strength is determined to be proportional to slope of a distribution of ship breadth. Numerical calculation is made by changing heel angle and drift angle systematically. Calculated values are compared with the experimental results presented by Son and Nomoto. It seemes that the approximate calculation method proposed here is useful for understanding a tendency showing variation of the hydrodynamic forces with heel angle.
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Tetsuya HAMANO, Roby KAMBISSERI, Yoshiho IKEDA
Article type: Article
Pages
143-148
Published: September 25, 1997
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This paper contains the study on the static and dynamic effects of flooded water on the stability of damaged ships. Model experiments with different amounts of water in its compartments and with a damage hole are carried out to find the influence of the water inside the ship and a damage hole on the motion and damping of ships. These experiments show that the effect of flooded water on the roll motion of ships is to reduce the amplitudes at reasonance due to increase of the roll damping. The damping is found to be more for the upper-deck flooding than for the below-deck flooding. In some upper-deck flooding cases, quasi-static heel, which is time average roll angle, is observed and is different from static heel in calm water.
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Toru KATAYAMA, Yoshiho IKEDA
Article type: Article
Pages
149-156
Published: September 25, 1997
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The longitudinal dynamic instability in calm water, porpoising, of a personal water craft is experimentally investigated at up to Fn=6.0. The criteria of occurrence of porpoising are predicted by using a linear stability theory. The porpoising motion is also estimated by using a non-linear time domain simulation method. The measured restoring, added mass and damping coefficients are used in these methods. The predicted criteria and the simulated motion are in good agreement with the measured ones. In order to reveal the cause of porpoising instability, the measured forces are analyzed. The results show that the coupled heave and pitch restoring coefficients have different sign and in the same order as the other coefficients in high advance speed range. This means that the porpoising is caused by a self-excited oscillation due to the energy exchange between heave and pitch motions.
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Kenjiro NABESHIMA, Masakazu OMOTE, Akira UENO, Hirotaka YAMAMOTO, Taka ...
Article type: Article
Pages
157-165
Published: September 25, 1997
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A new type rudder "VecTwin" has been arisen and 25 sets of it supplied for various kinds of ships in Japan. All of the ones show good manoeuvring movements such as free berthing and unberthing in short time, station keeping, short stopping distance, shiphandling with very low speed, spin- like turning by aiding a bowthruster, shiphandling in astern running and so on. The movements can be done with keeping propeller rotating ahead. In a voyage of rough sea condition, she keeps straight course with small helm corrections. Actual results of the VecTwin ships are dealt here for evaluating the manoeuvring performances.
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Ritsuo SHIGEHIRO, Kohei UEDA, Toshihiko ARII, Hiroshi NAKAYAMA
Article type: Article
Pages
167-174
Published: September 25, 1997
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The high-speed-towed fish preserve is a new type vessel about 15.6 m long with a fish preserve capacity of 200 m^3. The vessel is supposed to be towed efficiently with a lighter draft (about 0.8m) at a maximum speed of about 10 knots (Fn=0.42). The lateral area ratio between a super structure and a hull is about 5.3 in a lighter draft. The course stability of the vessel might be affected by the wind forces and wave forces. Especially the wind forces are stronger than wave forces in a lighter draft. In this paper, we present the course stability characteristics of the towed fish preserve with wind forces in a lighter draft. We conducted the model experiment tests in a wind tunnel and in a circular tank. The model scales are 1/55^<th> (0.284 m) for the wind tunnel and 1/25^<th> (0.624 m) for the circular tank. Also we performed the simulation studies to investigate the course stability for our mathematical mode. The results of our experiments and simulation studies are described and discussed.
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Yasumi TOYAMA, Tomoko AKASHI
Article type: Article
Pages
175-180
Published: September 25, 1997
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This paper focuses on the method of vibration analysis of a wetted bottom structure of a narrow tank in ships. The natural frequencies of a simply supported bottom panel are analyzed by means of analytical energy method, boundary element and finite element techniques. Comparing the results, the numerical accuracy of the natural frequencies depending on the methods and mesh sizes has been investigated. The vibratory responses of the bottom panel are also analyzed in the case where the tank is enforced to vibrate in vertical direction with given acceleration.
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Osamu MURAGISHI, Takao YOSHIKAWA, Atsushi SANO, Akira KOHSAKA, Shunjir ...
Article type: Article
Pages
181-189
Published: September 25, 1997
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An airplane or its engine was possibly supposed to drop on a large floating structure, which is planned to be a marine airport and mainly constructed with steel and paved with concrete slabs. The damage of the floating structure with and without concrete pavement was investigated by numerical simulation. A non-linear dynamic finite element analysis program with explicit integration, LSDYNA3D, was utilized to calculate the behavior of concrete fracturing. By simulation, the colliding phenomena, absorbed energy on the deck, and penetration were calculated. It was found that the concrete pavement was effective to increase energy absorption against an engine collision and the assumed construction of deck was strong enough against airplane collision. A simplified model for the parametric study of structural design was introduced.
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Isao NEKI, Tsuyoshi TADA
Article type: Article
Pages
191-197
Published: September 25, 1997
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A New Finite Element by Source method, or FES, has been developed by the authors. FES which has flexible geometrical shape is composed by nodes distributed on the element boundary and sources distributed out of the element boundary. The relation between the intensity of sources and the boundary condition at the nodes is obtained from the combination of the fundamental solution. According to this procedure, we can perform numerical analysis dealing with complex structures such as ships with further less mesh compared with the traditional finite element method and we can obtain more accurate results. This paper presents the application of plate elements for three-dimensional plate structures and some numerical examples to actual ship structures in order to show its usefulness.
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Toshihiko FUNAKI, Shigehiro HAYASHI, Yoshio HIRAI
Article type: Article
Pages
199-204
Published: September 25, 1997
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In this paper, the new method to estimate the ship vibration characteristics in the deep water from results of the experiment in the shallow water is shown. This method is structural modification analysis using dynamic stiffness matrix defined as inverse matrix of transfer matrix. And authors have investigated the advantage of this method in comparison with traditional structural modification analysis using eigenvalue method.
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Toshihiko FUNAKI, Shigehiro HAYASHI, Syunji UEDA, Naruyoshi IZUMI
Article type: Article
Pages
205-210
Published: September 25, 1997
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Not only natural frequency but also vibration level around the peak frequency should be calculate when the vibrational performances of the structure, which is excited by dynamic forces, are estimated. If one of the vibration levels around peak frequencies violates the permissible limit, the structure must be redesign to satisfy the permissible limit. Therefore it is useful and important for designer to obtain the sensitivity distributions for the vibration levels around the peak frequencies, because he can know how to efficiently modify the structure. In this paper, to obtain previous sensitivities, the word of 'Peak Level' is defineded as the vibration level at the natural frequency and the sensitivity of the peak level is formulated. Then the sensitivity of vibration level around peak frequency is formulated with considering angular frequency around peak as the function of the design variables. Besides the validity of these formulations is verified by comparing the accurate solutions of the simple mass-spring model.
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Kouhei MATSUMOTO, Toshimasa SAITOH
Article type: Article
Pages
211-218
Published: September 25, 1997
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Vibration checks to avoid harmful vibration of ships are usually carried out at various stages of a ship design. By using several vibration analysis, resonance check method or allowable vibration level limit method are usually applied to present designing. There are some kind of vibration analysis method to estimate natural frequencies or vibration response level such as 3D FEM, method by simple models and empirical formulas. In order to design by an effective check procedure, it is important to choose reasonable combination of objective vibrating structure, exciting forces, vibration analysis method and an applied rule for design judgment. In this paper, authors proposed a new design check procedure based on various databases constructed by data of ever-existing ships and utilized vibration analysis computer softwares on the inter/intra-network. Some problems concerning about vibration analysis are also described.
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Koji MASAOKA, Wataru KIYOKAWA, Campos Alejandro L. Talavera, Hiroo OKA ...
Article type: Article
Pages
219-226
Published: September 25, 1997
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As a part of the study on the structural reliability analysis of marine plate structures, this study deals with the simplified collapse and reliability analysis using 8 node hexahedral element models. Firstly, marine plate structures are replaced with hexahedral element models having the equivalent strengths under combined inplane stresses and lateral pressure. Secondly, the behavior of failed elements is derived by applying the simplified and efficient methods using the linearized failure condition and a plastic node method based on the plastic potential theory. Finally, the validity of the analytical system is demonstrated by giving numerical examples on a double hull box girder with longitudinal stiffeners under several loading conditions.
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Takashi TSUBOGO, Hiroo OKADA
Article type: Article
Pages
227-234
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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A number of studies on the dynamic structural analysis of huge floating structures with length or breadth to the order of several thousands of meters have been done by several authors. Most of these studies deal with the basic characteristics of vertical deflections of the structure modeled as a beam or plate on elastic foundation. Eigen frequencies for vertical vibrations of very large and comparatively flexible floating structures exist continuously in relatively high frequency zone due to buoyancy effect. On the other hand, the lowest eigen frequency for horizontal vibrations may appear in the lower frequency zone than the heave-mode frequency, because of no effect of buoyancy on the horizontal deflection behaviour. 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 behaviour for the horizontal deflection of a huge floating structure (about 4,600m×1,000m) using the beam model cosidering shearing rigidity by the analytical method. Effects of mooring characteristics and structural parameters on the dynamic response and strength of such structures are discussed. The results obtained in this study are summarized as follows: (1)It is comfirmed that the lowest eigen frequency for horizontal vibrations of the huge floating structure is comparatively lower than the heave-mode frequency and intervals of eigen frequencies are wide. (2)It is pointed out that not only vertical deflection behaviours but horizontal deflection behaviours should be also considered at the lower frequency zone. (3)It is neccessary to consider effects of shearing rigidity on the horizontal deflection behaviour.
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Takashi TSUBOGO, Hiroo OKADA
Article type: Article
Pages
235-242
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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Recently many studies on the elastic response behavour of very large floating structures have been done. Such a very large structure is relatively flexible compared with real floating structures like large ships. For estimating the dynamic response behaviour of the structure, it is important to consider the deflection wave propagation based on fluid-structure interaction analysis. In this study, in order to improve the overall response of a very long floating structure (about4600m×1000m), the effects of the axial force by mooring or towing, Tension Leg (TL) and the bending rigidity of the structure on dispersion relation of deflection wave propagation and frequency response are investigated. Firstly, dispersion relation of deflection wave propagation is derived on the analogy of liner water wave theory. Next, by using this dispersion relation, the effects of those on wave length (or dispersion relation) of deflection wave propagation are investigated. From these results, it is shown that the effects of TL in lower frequency zone than the characteristic frequency and bending rigidity in higher frequency zone than the characteristic frequency on deflection wave propagation and frequency response characteristics are remarkable.
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Shinsuke AKAGI, Hiroyuki TADA, Fumio NAKAHATA, Kikuo FUJITA
Article type: Article
Pages
243-252
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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Transport economy for a fast ferry carrying passengers, cars and trucks was evaluated from the view point of ship design. A SWATH (Small Waterplane Area and Twin Hull) type fast ferry was selected for the evaluation. Firstly its hullform was optimized to minimize total resistance. After that, its transport cost and fare were determined for several transport routes to evaluate competitively with other transport means, i.e., conventional ferries, land transports, air transports etc. It was found that the fast ferry has enough potential to be operated competitively with other transport means in several coastal routes along the Japan Islands.
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Tsugukiyo HIRAYAMA, Isao KAWAUCHI, Takehiko TAKAYAMA, Kiyoshi MIYAKAWA
Article type: Article
Pages
253-260
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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As directional wave buoy, so called Roll-Pitch-Buoys are well known, but they are not easy to hundle. So, a small, easy to hundle and cheap directional buoy is required for short term wave measurement, for example, in ship trials. Here, we developed a such kind of small directional buoy for short term measurement, evaluating its possibility by tank experiment and carrying out field measurement.
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Koji OTSUKA, Yusuke TAHARA, Yoshiho IKEDA
Article type: Article
Pages
261-267
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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In this paper, two-dimensional Navier-Stokes simulations for a very flat rectangular body in a steady current with Reynolds number of the order of 10^8 were performed, in order to investigate shallow water effect on current force acting on a pontoon-type very large floating structure. The results showed that the total current force consists of frictional drag on the bottom surface, pressure drag due to pressure loss in the region beneath the structure, and the pressure drag due to separation. The shallow water effect on these three drag components can be theoretically estimated by considering fluid velocity acceleration in the region beneath the structure. The current force acting on a floating structure with length of 5000 m was also estimated by the present estimation method.
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Katsuji TANIZAWA, Shigeru NAITO
Article type: Article
Pages
269-274
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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In this study, a numerical approach is taken for the fully nonlinear analysis of the interaction between an incident wave and low-frequency oscillatory motion of a floating body. Using the fully nonlinear simulation method, three motions of a moored two-dimensional body are simulated in presence of a regular wave field and the hydrodynamic force due to the interaction is extracted from horizontal hydrodynamic force act to the body. Based on this numerical study, added mass and damping coefficient due to the interaction are analyzed and a rational explanation of wave-drift damping is proposed. The relation between this explanation and the conventional explanation based on quasi-steady analysis is discussed.
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Article type: Appendix
Pages
App2-
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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Article type: Cover
Pages
Cover2-
Published: September 25, 1997
Released on J-STAGE: April 01, 2018
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