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Article type: Cover
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Published: September 25, 1993
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Article type: Index
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Published: September 25, 1993
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Article type: Index
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Published: September 25, 1993
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Masatoshi BESSHO, Shun SAKUMA
Article type: Article
Pages
1-6
Published: September 25, 1993
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A theoretical study concerning the residual resistance of a high-speed ship with shallow draft and transom stern has been carried out by Bessho using the linear wave-making resistance theory. In this theory, singularities around the forward periphery of the water plane are introduced to satisfy Kutaa condition at aft end imposing the condition the ship has a vertical stem and the water plane does not vary with speed. this singularity is known as a line-integral singularity in the linear wave-making resistance theory. The numerical verification about two dimensional problems and three dimensional gliding plates has been carried out. This report deals with numerical verification on a three dimensional shallow draft ship. The comparison of the numerical result with experimental data shows a slight difference. However, the theory presents good interpretation of the phenomena.
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Yoji HIMENO, Susumu HIRANO, Kazuhiro KITAGAWA
Article type: Article
Pages
7-16
Published: September 25, 1993
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The present paper describes a method of predicting the hydrodynamic characteristics of high speed planing hull form by using a linear water-wave theory based on Neumann-Kelvin approach. The method is to solve numerically the source density distribution on the bottom hull, in which computational method of calculating wave Green function based on an approach using complex exponential formula. The computation is applied to a wedge shape planing hull form. The results of pressure distribution, pressure resistance, and wave resistance are in good agreement with the measured data which were obtained by the authors.
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Shigeaki SHIOTANI, Michio NAKATO
Article type: Article
Pages
17-27
Published: September 25, 1993
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This paper deals with numerical computational method on three-dimensional surface waves which are generated by a running pressure disturbance. The computational method by modified IAF scheme is investigated. The characteristics of this computational method are that the three dimensional Navier-Stokes equations are treated including viscosity terms, that the distribution of a pressure disturbance is arbitrary and that the computing efficiency is very superior compared with the ordinary MAC scheme in this problem. The validation of computational results by this scheme is investigated by comparison with results obtained by MAC scheme. The calculations of wave pattern generated by running pressure of various distributions are tried.
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Yusuke Tahara
Article type: Article
Pages
29-47
Published: September 25, 1993
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Ship boundary-layer and wake flows are analyzed by the finite-analytic scheme. The Reynolds-Averaged Navier-Stokes equations are solved with the standard k-ε turbulence model and the wall-function approach. The numerical method developed by Patel et al for calculating ship stern and wake flows has been modified and extended to analyze a wider flow region with a more general hull geometry. An overview is given for the present approach and numerical results are presented for the Series 60 model. The latter includes detailed comparisons between the present and previous computational results with available experimental data.
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Kazuki YABUSHITA, Yasuyuki TODA, Toshio SUZUKI
Article type: Article
Pages
49-55
Published: September 25, 1993
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On a regular mesh the 4-points finite analytic method is presented for uncompressible viscous flow around a two-dimensional finite flat plate. At this time it is assumed that pressure distributions is expressed by a quadratic equation on the grid. Consequently smooth pressure distributions can be obtained. The subsequent algebraic matrix is made from the Navier-Stokes equations and a continuity equation, and so solved directly at the same time. The results of a flat plat at 0° incidence are calculated for the steady and surging motion cases. And the results of 90° incidence are exhibited for the sudden starting and uniformaly acceleration. The vortex length of the two cases are agreed with Taneda's experiments.
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Minoru INOUE, Nobuhiro BABA, Yoji HIMENO
Article type: Article
Pages
57-64
Published: September 25, 1993
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The characteristics of free-surface turbulence are investigated by experimental and numerical analysis of the viscous flow field around an advancing vertical circular cylinder piercing free-surface. The wave height and flow velocity are measured with a wave height meter of servo type and a hot-film anemometer, respectively. The numerical method used here is the three-dimentional finite volume method to solve the incompressible viscous flow with the free-surface using the free-surface fitted coordinate system. The results reveal the strong interaction of the nonlinear water wave with the separated vortical flow behind the circular cylinder. Some features of the viscous flow field change in the vertical direction by the deformation of free-surface waves. The vertical variation depends on the Froude number as well as the Reynolds number. At deep level the vortex shedding occurs periodically, while at shallow level this periodic phenomenon is not clear under the effect of steep waves with turbulence. The free-surface turbulence starts to appear at the points where the wave gradient vanishes. This result suggests it is attributable to the inherent instability of free-surface.
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Kazuhiko TUNOO, Toshio SUZUKI
Article type: Article
Pages
65-70
Published: September 25, 1993
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Laser or white light speckle photograph method is one of the very useful techniques to measure velocity field. The speckle photographs are usually lighted by fine laser beams and generate the Young's fringes. Velocity vectors are analysed by counting the fringe spacings and directions using Fourier Transform method or the others. In this paper, Fast Fourier Transform (FFT) method is applied to analyse the speckle photographs directly. Two kinds of simplifying methods, named one dimensional FFT method and one dimensional compressing method, are also introduced to shorten the analysing time. Three methods are applied to analyse flow field around a circular cylinder. Obtained results are as follows; (1) Good agreements are obtained between the three methods except separated flow region. (2) The one dimensional compressing method spend significantly shorter analysing time, round 1/10, than the others.
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Umesaburou KAWAHARA, Katsuo SUZUKI, Kazuki YABUSHITA
Article type: Article
Pages
71-82
Published: September 25, 1993
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An apparatus is newly deviced for measuring resistance, trim moment and rise of the center of gravity of a high-speed boat model with trim fixed. The experiments using the dynamometer are conducted in the circulating water channel and the results are compared with the data of the resistance test with trim free. It is revealed that resistance, trim angle and rise of the center of gravity of the freely towed model can be analyzed from trim-fixed test measurments, and that the effects of variation of initial trims, tow angles and heights of towing point in the trim-free test can be easily estimated. A rational method is proposed for predicting using trim-fixed test results to obtain full-scale performances of boat. The results analyzed are also available for comparing with theoretical methods and for development of boat forms.
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Keiichi KARASUNO, Jiro KUBOTA, Syunji JANUMA
Article type: Article
Pages
83-95
Published: September 25, 1993
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The service speed of small fishing boats have grown faster recently. Nowadays, there are some fishing boats runnnig over 25 knots (F_n>1.0). To survey the resistance and running trim of these small high speed crafts, the towing tank tests are carried out. This paper has investigate the techniques of the towing test for small ship models in free towing with high speed and the mutual relations of the test results between free and fixed towing motions of heaving and pitching. As the results, one of the conclusions of this paper is that the change of the displacement measured by the free towing test is equal to the lift force measured by the fixed towing test. This conclusion was derived from the physical simulations using free towing models loaded counter weights of the lift force measured by the fixed towing tests.
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Yukihiko OKAMOTO
Article type: Article
Pages
97-103
Published: September 25, 1993
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Four propellers with different skew angle distribution and constant pitch distributions are selected in order to clarify the skew effects on hydrodynamic characteristics of propeller performance. Using these propellers, the effects of the skew distributions on propeller open-water characteristics, cavity extents and cavity thickness distributions on the suction side of the propeller blades are investigated by towing tank tests and cavitation tests in uniform flow. The test results show that the increase of skew angle induce the increase of thrust and torque coefficient, but only slight changes in efficiency. The cavity extent and thickness near the blade tip also increase in proportion to the increse of skew angle. The potential-based vortex lattice calculations have been done to obtain detail informations from the calculated flow field around the propeller blades in non-cavitating condition. Cavity extents and thickness distributions are also calculated by linearized free streamline theory and compared with the experimental results. These results show that the propeller loading near the blade tip increases and the loading near the root decreases as the increase of skew angle. The calculated cavity thickness distributions near the blade tip are underestimated but those of inner part are overestimated.
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Toshiho SUZUKI, Kazuya SUMINO
Article type: Article
Pages
105-110
Published: September 25, 1993
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It is generally known that the light from the bottom of tank is refracted when it passes through water surface. So the light distribution projected on a screen near the wave surface has strong relation with the wave height and pattern. This report describes about the relation between them and it propose a new technique to mesure wave height from the light distribution using the relation. The light distribution is represented by second order differentials of wave pattern, and the pattern is calculated using the Fast Fourier Transform method. Obtained results show good agreement when the screen is arranged near the water surface.
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Ken TAKAGI, Shigeru NAITO
Article type: Article
Pages
111-120
Published: September 25, 1993
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In order to investigate the mutual relation between the above water hull form and deck wetness, experiments are carried out with three models of which above water hull forms are different. Measurements of heave motion, pitch motion and the vertical acceleration at F.P. are performed in regular head waves and the wave steepness is varied. The behavior of the free water on the deck is recorded with a video camera. Measurements of absolute bow motion, relative bow motion and deck wetness in irregular waves are also performed. Results show followings. The effect of the above water hull form on the motion and the acceleration is small. The difference on deck wetness performace is not obvios, however the behavior of free water varies with the above water hull form. The long time experiment is needed to confirm the statistical property of deck wetness in irregular waves.
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Keiichi KARASUNO, Kouichirou TAKANO
Article type: Article
Pages
121-127
Published: September 25, 1993
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The knowledge of added masses m_x and m_y is important to estimate not only ship's accelerating motions but also unstable yaw-moment (m_x-m_y)・u・v called as Munk-moment. In order to estimate the added masses of a ship, "Motora-charts" estimating the added masses are available for ships with usual forms. But they may not give the suitable estimation for other ships with unusual forms, for example small fishing boat or pontoon with rectangular. In order to measure the added masses m_x and m_y of these unusual ships in steering motion by experiments, this paper developed the experimental and analysing techniques of the oblique towing-test with constant acceleration for a ship -model. As the results, it becomes easy to measure at once both of two directional added masses m_x and m_y one oblique-twing test with one drift angle.
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Kazuhiko HASEGAWA, Yoichi FUJITA
Article type: Article
Pages
129-133
Published: September 25, 1993
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The extended system of Ship Auto-navigation Fuzzy Expert System (SAFES) is proposed, which is applicable even for narrow and congested waterways. SAFES is an expert system using fuzzy reasoning and control as well as regulations, captain's experiences and knowledge as knowledge bases. It also includes the visual information understanding for waterway boundary detection. The system is applied for safety assessment of a waterway design, combining with marine traffic simulation system. In this method, the assessment can be done qualitatively, quantatively and statistically. The alternatives of waterway design can be evaluated, considering the effect of traffic.
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Kazuhiko HASEGAWA, Keiji KITERA
Article type: Article
Pages
135-143
Published: September 25, 1993
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Automatic berthing system for ships using neural networkand knowledge-base is developed and confirmed its availability by simulation. Three layer neural net work is used and error back propagation method is employed for learning of weighting factors and offsets. According to the simulation, it is verified to get the successfull results not only for the given pattern as teaching data but also for interporated or exterporated cases. It is further confirmed to work satisfactorily even under the wind disturbance.
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Ryusuke HOSODA, Mitsuo KISHI, Tomoki YAMADA, Masakazu ARIMA, Takeshi N ...
Article type: Article
Pages
145-151
Published: September 25, 1993
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The authors introduce a ship-motion simulator which will make it possible to carry out experimental studies on motion-sickness and ride-quality of ships and other vehicles. The purpose of the laboratory experiments by using the ship-motion simulator is to make clear the mechanism of the motion-sickness incidence. For this, it is necessary to carry out many experiments under the same situational conditions. Physiological measurements such as electroencephalogram, electrocardiogram, sweating, blood pressure and pulse, as well as facial expressions of subjects exposed to low frequency whole-body oscillation. At the same time, psychological changes of the subjects during the oscillations are also measured. Some examples of measured results are reported in the paper.
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Houqin ZHC, Jijia ZHENG, Yao ZHAO
Article type: Article
Pages
153-158
Published: September 25, 1993
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Rigid plastic dynamic analysis is used for predicting the structural behaviour of struck vessels. The idealized collision scenario is a rigid, vertical bow striking a tanker at a right angle, midway between rigid bulkheads. The structures, speeds and sizes of ships are considered. Finally, an experiment is made in order to verify analysis.
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Kanta NIHEI, Fumihide INAMURA, Shigeki KOE
Article type: Article
Pages
159-166
Published: September 25, 1993
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There is a hot spot stress (H.S.S.) method where a unified S-N curve is used instead of many curves corresponding to joint category for the estimation of fatigue strength of welded structures. In this paper, the hot spot stress method, which is more reasonable and simpler than before, is being discussed for the welded plate structures, ship hull structures, the bogie frame of the rolling stock, etc. First, stress analysis of simple fillet welded models were carried out, by means of boundary element method (BEM) to investigate a simpler calculating method of hot spot stress. As a result, it was found that stress concentration due to weld bead is nearly reduced to zero at the point about 30% thickness of main plate off the weld toe, so long as the plate thickness (t) is within the range used for welded plate structures (3mm<__=t<__=18mm). The authors propose, herein, a simplified H.S.S. calculating method by defining H.S.S. as a stress at 0.3t from the weld toe (0.3t method) for, mainly, ship hull structures. In order to verify the validity of this calculating method of hot spot stress (0.3t method), the fatigue tests have been carried out for two types of the fillet welded joints, i.e., cruciform-tension-type and T-bending-type fillet welded joints. Each type has global stress concentration or no global stress concentration due to the structural discontinuity. But each type has the same local stress concentration due to the weld bead shape. As a result, all S-N data based on hot spot stress range by the 0.3t method gathered within a narrow band independent of structural stress concentration factors. And it has been confirmed that the 0.3t method is applicable for unified fatigue strength estimation of fillet welded plate structures.
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Shinsuke AKAGI
Article type: Article
Pages
167-176
Published: September 25, 1993
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The transport economy for high speed marine vehicles is discussed in succession to the previous paper. In the previous paper, the transport economy of high speed marine vehicles was discussed from synthetic aspects for both economy and vehicle performance. In this paper, their transport economy is treated from a view point of market research. Firstly, a systematic procedure for the market research of the high speed marine vehicles is introduced by considering their share when they are operated competitively among other various transport systems. After that, their direct operating cost is analyzed in connection with the key factors of vehicle design, i.e., vehicle efficiency etc. Finally, a market research for high speed marine vehicles is presented for applying them to the Seto inland sea area.
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Masahiko MORI
Article type: Article
Pages
177-184
Published: September 25, 1993
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Demand for the size and hull form of newly-built ships is diversified under the age of a low economic growth. The author has developed how to design a new full ship to meet the diversified requests from shipowners and the basic performance of the ship. The core of this method is to design a new full ship with the different length, breadth, depth and draft from those of a prototype ship, by keeping its aft and/or fore part as originally same as possible. The feature is aimed at the individual characteristics of three parts of the ship, that is the entrance, the run and the parallel part, which affect the hull resistance and the self-propulsive performance. An example of application and the design system to develop this method are also presented.
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Hikaru YAGI, Hikaru KAMIIRISA
Article type: Article
Pages
185-191
Published: September 25, 1993
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The integrated duct propeller has been introduced as a fuel saving device of large full ships since 1978. It is featured that the duct is located in front of the propeller and secured to the hull with structural integrity. In one case of a 132,000 dwt bulk carrier among many full scale measurements, self-excited vibration of duct was found. The study was made to investigate the dynamics of flow as well to evaluate possible countermeasures. Duct tail fin was selected and its effectiveness was confirmed on the actual vessels as was estimated by the model tests.
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Shigeru NAITO, Munehiko MINOURA
Article type: Article
Pages
193-199
Published: September 25, 1993
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We have two methods to generate an irregular wave numerically. One is summation methods by summing up regular waves, another is the convolution integral method by the linear system theory. In the later method, the kernal function and a white noise usually are used. We succeeded to obtaine the kernal function analytically, namely impulse response function, in the time domain of Peirson-Moskowitz (P-M) type spectrum. This function is important to generate an irregular wave with the convolution integral method. We confirmed this function is correct as follows that the spectrum of irregular waves generated numerically with this function and white noise agree with the given P-M type wave spectrum well.
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Toru HACHIWAKA, Yoji HIMENO, Nobuhiro BABA
Article type: Article
Pages
201-210
Published: September 25, 1993
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Numerical experiments on the tidal current of M_2 tide in Osaka Bay are carried out using 2D and quasi-3D models. The computed results such as the instantaneous velocity field, tidal residual current, and hodographs are compared with those calculated from the observed data. The 2D model gives important features of actual tidal current in Osaka Bay such as the formation of stagnant region in the east part, twin vortices in the vicinity of the Akashi Straits, Okinose Circulation and Suma Offshore Counter Current, but it would compute much higher flow speed at the Straits. The Quasi-3D model which includes the submarine topograph could improve the above defect and realize Tomogashima Counter Current and East Coast Southward Current as well, but it would compute too high flow speed on the shallow region in the east part even though the bottom friction is taken into account. At spring tide the twin vortices formed at the Straits when the flow through the Akashi Straits is eastward maximum travel to the middle part of the Bay, and get the energy to continue rotating from the northward current along Awaji Island when the flow through the Akashi Straits is westward. At neap tide the vortices stay near the Straits and disappear at the turn of tides. When the twin vortices are shed from the Straits, they lose the symmetrical feature and eventually remains as Okinose Circulation and Suma Seashore Counter Current. Fractal dimensions for flow phenomena in Osaka Bay are estimated using the observation data. The result suggests the chaotic characteristics of actual tidal current makes its long-term prediction very difficult.
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Koji OTSUKA, Koki IKEDA, Yoshiho IKEDA
Article type: Article
Pages
211-216
Published: September 25, 1993
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Inertia force on a horizontal circular cylinder in waves significantly decreases with increasing Kc number at low Kc number. The authors reported that the inertiaforce reduction of the horizontal cylinder can be explained by using a simple vortex shedding model. On the basis of this model, it was deduced that the inertia coefficient in regular waves is given by a simple formula, Cm=2-(2/π^2)Kc^2. In this paper, the formula is extended to an inclined cylinder horizontally submerged in regular waves. The extended formulas are in good agreement with the experimental results at Kc less than 2.5 for any inclination angle.
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Ken TAKAGI
Article type: Article
Pages
217-223
Published: September 25, 1993
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A nonlinear theory is developed in this paper to analyze the drift force on a rectangular body close the free surface. The overall problem is divided into three parts wihich are an external outer region, an internal outer region and an inner region. Solutuins of these problems are matched each other by means of the matched asymptotic expansion procedure and the solution is harmonic in time. This theory satisfies the conservation of the wave energy. Some numerical results show that the negative drift force occurs at a certain frequency. Some experimental results also show the possibility of the negative drift force.
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Kenji YAMAKAWA, Shoichi HARA
Article type: Article
Pages
225-232
Published: September 25, 1993
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The full-scale experiment has been carried out using the proto-type offshore floating platform of column-footing type (L×B×d=34m×24m×5.5m) named "POSEIDON" at 3km off of Yura port, Tsuruoka city, Yamagata prefecture for 4 years from 1986 to 1990. The experimental structure was constructed at Naruto city, Tokushima prefecture and was towed about 900 nautical miles all the way to the experimental cite. The towline tension has been measured during towing. On the design stage, the model experiment has been carried out in order to estimate the towing resistance and mameueverability. On the other hand, the measurement for the towline tension and the motion of the floating structure has been made during towing to Sakata port about 20 nautical miles north of the experimental site for scrapping the structure after finishing the experiment. The estimation for the average towline tension from the model test agrees well with the obtained results. As for the fluctuating towline tension, there exists the high frequency component wthich coincides with the wave frequency and the low frequency component. The average towline tension and the fluctuating towline tension are mainly discussed in this paper.
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Shoichi HARA, Kenji YAMAKAWA
Article type: Article
Pages
233-247
Published: September 25, 1993
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The towing experiment in waves using two types of model of offshore structures such as barge and semi-submersible has been carried out in order to investigate the effect of the towline length, towing speed, types of the towed vessels, sea state and the tow motion on the towline tension. The comparison between the towline tension of the hawser and the bridle has been done and the statistic analysis of the dynamic towline tension has been made. The applicability of the Hermite moment model to the statistic distribution of the towline tension has been discussed. Furthermore, the effect of the towline tension on the motion of tug and tow has mainly been investigated. The forced oscillation test with the towline cable model in still water has also been carried out to clarify the dynamic towline tension during towing. The experimental results have been compared with the theoretical calculation such as Fylling's simplified analysis, lumped mass method and Shin's method using clipping-off model. It is concluded that the Shin's method agrees well with the experimental results even in the case of the strong non-linearrty like a snapping.
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Article type: Bibliography
Pages
248-
Published: September 25, 1993
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Article type: Appendix
Pages
App1-
Published: September 25, 1993
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Article type: Cover
Pages
Cover2-
Published: September 25, 1993
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