-
Article type: Cover
Pages
Cover1-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
App1-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Index
Pages
Toc1-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Index
Pages
Toc2-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Masaru TSUJIMOTO, Munehiko HINATSU, Yoshiaki TSUKADA, Yoshimasa MINAMI ...
Article type: Article
Pages
1-9
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
There is an estimation and evaluation method for ship performance in actual seas based on a probabilistic theory. However its investigation has not carried out enough, for the accuracy of weather measurements and the closed publication of voyage data. Here we conduct theoretical estimations based on a probabilistic theory in ship speed, fuel oil consumption and main engine power. Then the probability density function obtained by the present method is compared with the function obtained by voyage data, which are automatically collected every 10 minutes by T.S.Seiunmaru. As the results, we can indicate good agreements between both probability density functions. Moreover we propose an evaluation method of schedule keeping performance and voyage cost performance using the probability density functions.
View full abstract
-
Yukata TERAO
Article type: Article
Pages
11-15
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A wave devouring propulsion system(WDPS)is a thrust generator of a ship and also used as a motion stabilizer, which converts wave energy directly into trust and efficiently reduces the hull motion in the waves. The WDPS concept consists of the hull and hydrofoil system. Generally one solid hydrofoil system is set in front of The ship bow and connected to the hull with pin joints and supported with soft springs to give the restoring force about the foil pitch motion. The experimental results of a newly designed dual fin type WDPS and hydrodynamic wave forces acting on the foils are shown in this paper. In the previous discussion of WDPS, which is related to the mechanism of thrust generation of single hydrofoil located at the incident waves, the heading sea condition is more suitable than any another wave direction. But the newly developed WDPS test shows that the fastest speed is achieved with a beam sea condition.
View full abstract
-
Nobuyuki HIRATA, Takanori HINO
Article type: Article
Pages
17-24
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A primary objective of the present work is to compare and evaluate the performance of several improved one-equation eddy viscosity models which are simple and available for the promising unstructured grid method. Two types of ship flows were tested on the basis of Reynolds averaged Navier-Stokes equations coupled with four turbulence models: 1)the original Spalart and Allmaras(SA)one equation model, 2)the SA model with Spalart and Shur correction to account for the system rotation and/or streamline curvature effects, 3)the SA model with the cross flow modification proposed by SR222 project, and4)the SA model with the axial vortex correction suggested by Spalart. The flows investigated were unbounded turbulent flows around an SR196A tanker ship and a Ryukou-maru tanker ship, respectively. The numerical results were compared with the measured data and computations using two of algebraic zero-equation eddy viscosity models, and the capabilities and limitations of the models to viscous flows around a ship hull, especially turbulent wakes, are discussed.
View full abstract
-
Yasuhiko SUGII, Taketoshi OKUNO, Shigeru NISHIO
Article type: Article
Pages
25-30
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In order to improve the resolution and accuracy, a number of iterative methods have benn proposed, in which re-correlation using the result of initial correlation with discrete window offset is applied. However, in the flow area with large velocity gradient, such as shear flows, compressible flows and turbulent flows, these methods are not very efficient. Furthermore in these methods, the three-point Gaussian peak fit based on correlation method is usually used for a sub-pixel analysis. It is reported that the root-mean-square error of the techniques is of the order of only 0.1 or more pixels and the techniques require very high image density. In this paper, a new high-resolution PIV technique based on cross-correlation and gradient method is proposed. For pixel unit displacement iterative method is applied and then for sub-pixel displacement spatio-temporal derivative method is taken instead of the three-point Gaussian peak fit. The experimental parameters for cross-correlation can be optimized through generalizing the method as a dynamical system, and a sub-pixel displacement is evaluated using spatio-temporal derivative method. The present method is applied for the jet flow images.
View full abstract
-
Kenji OKIMOTO, Yoji HIMENO, Yusuke TAHARA
Article type: Article
Pages
31-40
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In the previous paper, the authors proposed a new κ-ε model and improved prediction accuracy of the mean flow field with longitudinal vortex. However, it was difficult to express normal Reynolds stresses accurately in view of Boussinesq assumption especially in high vorticity region. To improve this problem, the authors examined the nonlinear eddy viscosity expressions and combined them with the author's κ-ε model. Computation is performed around the SR196a ship stern form with the longitudinal vortex to clarify the validity of the nonlinear κ-ε model. The conclusion is that the nonlinear κ-ε model shows some improvements of the local trend of the normal Reynolds stress profiles.
View full abstract
-
Yusuke TAHARA, Ryuji NISHIDA, Jun ANDO, Yoji HIMENO
Article type: Article
Pages
41-50
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
This paper presents optimization of tanker stern form based on viscous flow information obtained from Computational Fluid Dynamics. In this 3rd report, main focus is placed on minimization of delivered horse power in conjunction with application of self-propulsion simulator, which is based on extension of a Reynolds-averaged Navier-Stokes(RaNS)equation solver including propeller effects evaluated by the infinite-number propeller theory. The overall numerical method follows that of earlier work(1st and 2nd reports), i.e., coupling of RaNS equation solver and successive quadratic programming. Constraints considered in the present study are basically same as those used in earlier work, i.e., geometrical requirements of optimized hull for displacement, profile, maximum beam and depth, and stern frame lines to secure enough space for engine room. In the following, details of the numerical mothod are described, and the discussion of the results includes identification of salient differences of forms and integral parameters between the original and optimized hull forms. 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.
View full abstract
-
Yusuke TAHARA, Yutaka YOSHIDA, Ryuji NISHIDA, Ryosuke MATSUI, Ichiro U ...
Article type: Article
Pages
51-59
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
This paper provides an introduction of ballast bulb development for International America's Cup Class(IACC)Sailing Yacht, that had been associated with the hull/appendage design project supported by Nippon Challenge Syndicate for the 30th America's Cup. In this report, main emphasis is especially placed on investigation on basic low drag form, which was one of research activities carried out by appendage design team. An overview is given for the Computational Fluid Dynamics design tool in association with the experimantal devices and procedures, then discussions are focused on important design aspects for prediction of laminar-to-turbulent flow transition occurs on the body at the full-scale-level Reynolds number.
View full abstract
-
Shigeru NISHIO, Yuki NARUSE, Taketoshi OKUNO
Article type: Article
Pages
61-68
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
An image measurement system of velocity field by means of statistical image analysis was developed. It was applied to a measurement of ship wake flow. Present technique is constructed with the fact that the provability of tracer particle passing through a target point in flow field is proportional to the concentration of particle and the flow speed. It enables to measure three-dimensional flow field using single CCD camera and laser light sheet. The principle of the measurement is describe by the constrain equation of visualized flow image, and it is extended to apply to the measurement in velocity vector field. The time-averaged flow speed distribution can be obtained by the present system. The time-averaged data is often useful in the engineering problems. The ship wake flow obtained by the present system shows the typical characteristics. The comparison of the measured results between the present system and the conventional Pitot tube show good agreement.
View full abstract
-
Hiroyuki KUDO, Hajime KIHARA, Seiji KINO, Hajime KOIZUKA, Syuko TAMURA ...
Article type: Article
Pages
69-77
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A plunger type of wave-absorbing-wave-maker was newly constructed in the wave tank of the National Defense Academy. The wave maker is controlled for absorbing reflected wave by the additional signal throught three digital filters, two of them for separating reflected wave by using two wave sensors and one for predicting the propagation time of the reflected wave and making wave cancelling the re-reflected wave from wave-maker. This idea of time-domain method for separating incident and reflected waves is due to Frigaard et al.(1994). The performances of absorbing reflected wave in periods 0.6 to 1.2 seconds are checked in some experiments by terms of re-reflected wave heights from the wave-maker, changes of added mass and dumping coefficients and the other values for a semi-submerged elliptic cylinder in both cases when fixed in waves and oscillated in sway motion in calm water and in the other cases. The absorbing efficiency is about more than 80% when the wave-maker is acting only for abosrbing incoming wave radiated from a oscillating floating body and more than 70% when for making incident wave. This discrepancy of the efficiencies is concluded to be mainly due to nolinear reflection properties of moving plunger.
View full abstract
-
Ken TAKAGI
Article type: Article
Pages
79-84
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
We propose an application of WKBJ approximation to hydro-elastic behavior of VLFS, since the method is not time consuming although the theory involve all environmental influence such as the bottom topology, break water and so on. The hydro-elastic behavior of VLFS is treated as wave propagation in the platform. This method is applied to the 5000m-class floating-airport with the variation of the bottom topology as an example. We also discuss on the average momentum equation beneath VLFS. Some interesting results about the set-up or the set-down of VLFS are derived. The formula of drifting force with arbitrary bottom topology is also obtained.
View full abstract
-
Masashi KASHIWAGI, Kazumasa KAWASOE, Masaru INADA
Article type: Article
Pages
85-94
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
It has been said that the strip method gives good prediction of ship motions at any rate, although hydrodynamic forces consisting of the ship-motion equation are not correctly predicted. To understand a reason of this wonder and a way of improvement in existing ship-motion theories, numerical results by NSM(New Strip Method) and EUT(Enhanced Unified Theory)are compared with experiments newly conducted using a modified Wigley model of L/B=6.667. Although the added mass, damping coefficient, and wave-exciting force in heave predicted by EUT are in good agreement with experiments, the heave amplitude by EUT is overpredicted particularly near resonance. It is found that a reason of this is due to improper prediction in the cross-coupling forces between heave and pitch, despite the value itself being very small. EUT also tends to overpredict the pitch damping coefficient and underpredict slightly the pitch exciting moment in relatively longer wavelength region;which results in underprediction of the pitch amplitude. Using experimental values for the cross-coupling added-mass terms(A_<53> and A_<35>)and the pitch damping coefficient (B_<55>), the results of EUT agree well with experiments of not only ship motions but also the added resistance in waves.
View full abstract
-
Yosuke SHIRAKURA, Katsuji TANIZAWA, Shigeru NAITO
Article type: Article
Pages
95-108
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A Numerical Wave Tank(NWT)for 3-D problems is developed. The motion of an ideal fluid and the motion of a floating body are simulated in a time domain. The Boundary Value Problems(BVP)for velocity field and acceleration field are solved taking into account the interaction between the fluid and floating body motions. The Quadratic Boundary Element Method(QBEM)is used to solve fields. Implicit boundary condition method is used for the acceleration field. Time integration is carried out with the 4th order Runge-Kutta method(RK4). Free surface is updated with the semi-Lagrangian time marchinng scheme. A double-node technique is used for proper treatment of intersections. Some calculations are carried out by a developed new 3-D NWT and the following three results are presented in this paper. 1.The simulation of 3-D waves in a circular wave basin. 2.The simulation of hydrodynamic forces on a sphere in forced heaving motion. 3.The simulation of the free jeaving motion of a sphere in a circular wave basin.
View full abstract
-
Yukata TERAO, Takeo NIKKO
Article type: Article
Pages
109-113
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
It is well known that whirling motion occurs when a ship is moored or towed with a single line. This motion causes not only excessive snap tension of the mooring or towed line but also the problem of course stability of the towing ship. We propose a new towing method, named the Kite Towing System, which needs no additional special equipments. It is a simple method of towing a ship or floating structure by the principle of kite stability, using the lift force, which is generated by the towed hull, and suppressing the whirling motion itself. This paper shows an analysis of this basic principle and results of self-running model experiments in a water tank. From these model examinations, the stability of the towed hull motion by the Kite Towing System is Proved.
View full abstract
-
Kensaku NOMOTO, Yutaka MASUYAMA, Akira SAKURAI
Article type: Article
Pages
115-124
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Since this type of sailing trader is a symbol of the prosperity of Osaka in Edo era, there is a good reason for the City of Osaka to reconstruct one in full-scale as a memorial. We took this opportunity to sail her to investigate the sailing performance of this remarkable vessel of genuine Japanese heritage some two hundred years back. The ship sailed to weather as high as 75° in her actual track with quite a good speed. This convinced us that they were the first real sailing trader in the history of Japan and fulfilled the great demand for carrying commodities in that era.
View full abstract
-
Munehiko MINOURA, Shigeru NAITO
Article type: Article
Pages
125-135
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A new concept of long term prediction of ship responses is introduced, where the ship responses are composed of the ship motions, wave loads and stresses casued by wave forces acting on the ship hull. In this prediction method, instead of the stochastic information of wave climate and the ship response function, the ship monitor data measured on board in some voyages is required. Furthermore a statistical model to carry out this prediction method is proposed and the long term prediction is executed with this model and the ship monitor data. The proposed statistical model is formulated by two probability distributions based on Fukuda's model. One distribution is the Rayleigh distribution for the extreme values of ship response, and the other three kinds of distribution for the standard deviation of ship response, which are assumed to be the Rayleigh, Weibull and Lognormal distribution. As a result it is cleared that the distribution of standard deviation corresponded with the Weibull or the Log-normal distribution, but the long term prediction did not always agree with the result of measurements. It is necessary for the more accurate prediction that the factors of voyage route, season, operation of navigation and storm are formulated.
View full abstract
-
Munehiko MINOURA, Shigeru NAITO, Kenichi SHIBATA
Article type: Article
Pages
137-145
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
It is possible to carry out the more detail long-term prediction of the ship responses, if the ship responses measured on board with the ship monitor system are estimated statistically. However we must pay attention to the characteristics of the ship monitor data which is the time history and is not so much we can get. To solve this problem and carry out the long-term prediction with a little of data, the statistical fluctuation of the ship response for a long term is necessary to be embeded in the statistical model. In this paper, firstly the existence of the seasonal effect in the ship responses for a long term is cleared with the spectrum analysis of the time series of the ship monitor data. Secondly the statistical model with the seasonal effect is proposed, and the long-term prediction is carried out with the ship monitor data. Finaly the smapling interval time of the ship monitor data to reduce the error of the prediction is investigated by using the periodical characteristics of the seasonal effect.
View full abstract
-
Shoichi HARA, Kenji YAMAKAWA, Kunihiro HOSHINO, Kazuhiro YUKAWA
Article type: Article
Pages
147-154
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
There occurred the oil leakage incident of the tanker named Erika at offshore of Brest in France December in 1999. The tanker has been broken into two parts and drifted resulted in sinking on the bottom of 120 m sea depth. The stern part of the ship has been towed toward the offshore in rough seas in order to protect the environmental protection of the coast. However, the fuel oil drifted from the tanker toward the coast and made a devastating damage on the coastline of the Biscay Bay. There also occurred Russian tanker Nakhodka oil leakage incident in the Japan Sea January in 1997. The drifted bow part of the tanker could not be prevented from reaching the seashore by the towing. Both oil leakage incidents are quite similar concerning the drifting of the wreck. There were quite a lots of incidents in the past in which disabled ships drifted to the seashore and oil leakage gave a tremendous damage. The authors have made a towing experiment both in still water and in regular head waves using a damaged model of geometrical ship form so far. They investigated the towline force and unstable motion during towing. They obtained the hydrodynamic coefficients during towing and analyzed the unstable motion solving the manoevoring equation together with the flow visualization techniques. They also compared the hydrodynamic force of the constrained model with the proposed estimation method resulting in a good agreement. In this report, the towing experiment on the condition of following waves has also been made as well as the head waves condition. The unstable motion and the towline tension increase in waves have been investigated experimentally.
View full abstract
-
Tsugukiyo HIRAYAMA, Kiyoshi MIYAKAWA, Takehiko TAKAYAMA
Article type: Article
Pages
155-165
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Today, flying boats are not used widely, but introducing high-technology of today, flying boats have new possibility that it can be used more widely, overcoming the defects existing in sea-keeping problems and corrosion problems of material by sea water. We planned to make improvement of sea-keeping quality of a flying boat on waves applying knowledge from ship and off-shore engineering. From this point of view, utilizing existing long wave tank, we tried to develop a high speed guiding system that can guide and supply electric power to a freely flying boat model and also to measure the motion of the model using wireless system. Furthermore we developed a lift augmenting system to the model wing simulating high lifting system by Boundary Layer Control(BLC)for actual planes. In this report, we describe about those systems and measured results of motions, accelerations and water pressure of a flying boat model during taking off and alighting both on still water and waves.
View full abstract
-
Hisafumi YOSHIDA, Seijiro MIYAKE, Hisao TANAKA
Article type: Article
Pages
167-172
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Rankine source method has been recognized as a practical computation tool for ship hydrodynamic problems in recent years. By using Rankine source method for the various seakeeping problems, such as ship speed decline in waves, wave-induced loads, and so on, improvements on the estimated precision of them can be expected. However, there are still some subjects to be settled like that optimal shape and arrangement of the free surface panel, difficulty in accurate computation of resistance increase in waves, etc. In this paper, authors paid attention on the insufficiency of the free surface panel resolution around the ship hull. To settle it, the computation method, which introduces the arbitrary panel topology on the free surface, was proposed. Computed results by present method were compared with experiments or other computation method for vaious ships, and it is shown that the proposed method can estimate fluid dynamic forces on the ship hull, and ship motions in waves with certain accuracy.
View full abstract
-
Masao KINOSHITA, Yukihiro TERADA, Hideshi KAKIMOTO, Hiroshi ISSHIKI, T ...
Article type: Article
Pages
173-177
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Higaki Kaisen which is the most popular Japanese sailing ship in Edo-era was restored by Osaka-city and was completed by hitachi Zosen Corporation in July, 1999. Naniwa-maru, the name of the ship, is 29.9 m in length and 150 t in displacement. To test the sailing performance, experiments were conducted in Osaka-bay for two weeks in the same month. To clarify the sailing performance, it is quite necessary to measure the ship position, speed and direction accurately. The high precision GPS has the accuracy of 2 cm, and is very suited for this kind of measurements. The measuring system using the high precision GPS and the results are discussed.
View full abstract
-
Yongkang MA, Toru KATAYAMA, Yoshiho IKEDA
Article type: Article
Pages
179-186
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In this study, the roll motion characteristics of a damaged ship in the intermediate stage of flooding are experimentally investigated. To confirm the results which is used to deduce the proposal of the damage stability requirement to improve the SOLAS regulation for a damaged ship submitted to SLF by the Netherlands, measurements of roll and heave motions of a model ship suddenly flooded into the midship section through a large damage opening are carried out. The results demonstrate that the proposal underestimates the maximum roll angle, and that the roll characteristics in the intermediate stage of flooding are sensitive to value of GM, deck arrangement in the damaged compartment, obstacles in the compartment, and location and area of a damage opening.
View full abstract
-
Hiroshi ISSHIKI
Article type: Article
Pages
187-191
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The action theorem discussed in the present paper gives the similar results for the uncoupled components(ex.sway component in heave motion)of hydrodynamic forces as the coupled ones. Greenberg and Cooperman combined the hyper circle method and Green's function and derived a method to obtain the upper and lower bounds of the argument function at an arbitrary point. According to the present method, a similar result not only for the value of the argument function itself but also for the derivatives of the arbitrary order can be obtained.
View full abstract
-
Seiya YAMASHITA, Tatsuo KABAYA
Article type: Article
Pages
193-198
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The characteristic features of hydro-elastic responses of a very large floating structure(VLFS)in waves are discussed. Simplified formulas are given for the wave number of structural deflection, char-acteristic wave number, and natural frequency for elastic-mode motion, which are basic parameters having significant influence on hydro-elastic responses of a VLFS. Dynamic behaviors of a VLFS in irregular waves are also investigated based on simplified formulas for structural deflection. It is shown that the response of structural deflection at midship in irregular waves, which is represented by the ratio of the significant value of the structural deflection to significant wave height, tends to be less dependent on the length of a VLFS as the length increases. This result is confirmed by illustrative computations using two-dimensional eigen-function method, and suitable diagrams for predicting the response of structural deflection of a VLFS in irregular waves are produced considering the result.
View full abstract
-
Masayuki OKADA, Yoshiho IKEDA, Toru KATAYAMA
Article type: Article
Pages
199-205
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
It is well known that for a high speed passenger ships a ride control system using trim-tabs or/and fins are very effective to reduce ship motions in waves and to improve comfortableness of passengers on the ship. In such a system, a conventional PID control is usually used. Ship motions of the scale model of a fast car-ferry with trim tabs under PD control in head waves are measured to assess the performance of the control system. The results show the trim tabs are not effective in shorter waves. In order to improve the performance of the control system in the region, a new hybrid control system is developed and proposed. In the system, the wave exciting pitching moment is estimated using a linear equation of motion using hydrodynamic derivatives predicted by an ordinary strip method, and is compared with the maximum moment created by the trim tabs. When the estimated exciting moment is smaller than the moment created by the trim tabs, the trim tabs are controlled to cancel the wave exciting moment, otherwise a PID control is adopted. These two control methods are automatically selected in the system. In order to confirm the effectiveness of the proposed system, a time-domain simulation using a non-linear coupling equation for heave and pitch is carried out in regular and irregular head waves. The results show the system can reduce ship pitch motions of a fast ship in head waves significantly.
View full abstract
-
Junya DOBASHI, Ken TAKAGI
Article type: Article
Pages
207-212
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Scale effect of water impact problem with trapped air is discussed in this paper. It is assumed that the sea surface can be expressed by a subsequence of circular hollows. Under this assumpution, the impact pressure with trapped air is investigated. Results show that the maximum value of the impact pressure becomes larger as the diameter of circular hollow increases. The effect of the trapped air on the impact pressure of the model scale is larger than that of the full scale.
View full abstract
-
Koji MASAOKA, Yasuhiro TSUKAMOTO, Takashi TSUBOGO, Hiroo OKADA
Article type: Article
Pages
213-219
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
This paper deals with a study on the collapsing behavior and reliability analysis of very large floating structures(VLFS)in irregular waves. First, a simplified estimation method is presented for collapsing behavior of VLFS by using Smith's method. Stress-strain curves of structural elements, which are used in Smith's method, are obtained by using finite element method considering large deflection and elasto-plastic behavior. Next, a simplified estimation method is shortly introduced for the dynamic response of the structure in irregular waves. Finally, the features of the collapsing behavior and reliability level are investigated by a numerical example applied to a 5, 000m class VLFS under trial design. Effects of statistical values such as reduction of thickness due to corrosion, yield stress and bending rigidity concerning with the expected value of maximum wave bending moment are also investigated by sensitivity analysis.
View full abstract
-
Hiroo OKADA, Hao LIU, Daisuke MATUMIYA, Koji MASAOKA, Takashi TSUBOGO
Article type: Article
Pages
221-227
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
This paper deals with the response behavior of ring-like hexagonal floating structures supported by columns in regular waves, as a part of basic studies on floating artificial islands. The response behavior of a basic structure model in regular waves is numerically obtained by using framed structure model on a elastic foundation. Then, in order to investigate the validity of numerical results by using the abovemodel, experimental studies are carried out for a basic model which is composed of vinyl chloride bar as the main structure with circular columns. Finally, it is found that the simplified estimation results are comparatively in good correspondence with the experimental results for the response behavior and strength of flexible ring-like floating structures supported by columns.
View full abstract
-
Nobutaka SHINKAI, Yasumitsu TOMITA, Naoki OSAWA, Kiyoshi HASHIMOTO, Ju ...
Article type: Article
Pages
229-235
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
The line-heating process has been used to form shell plates of ships and done only by skilled handwork of experienced workers. To make this process automatic, heat transfer phenomena between the combustion flame and the heat plate need to be analyzed. In this paper, high temperature jet instead of combustion flame is used to analyze the thermo-flow field during line-heating. Movement of a heat source is approximately analyzed by shifting a exit of jet. Turbulent model is κ-ε two equations model, and logarithmic law is assumed as wall functions. In conclusion, shifting a exit of high temperature jet is usuful to calculate the thermo-flow field during line-heating, and an efficient method to heat the same plate is considered.
View full abstract
-
Makoto ARAI, Taito SHIMIZU, Tatsuhiro SUZUKI
Article type: Article
Pages
237-243
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
When a ship designer carries out ship structural design, he first considers several combinations of design variables related to structural form, structural size, and so on. Next, he carries out response analysis using FEM or some other method, and estimates the performance of each design. Finally, he selects the best design from among the candidates. However, this design-selection procedure carries with it the possibility that the selected combination of design variables may not always be the optimal one, due to the limited number of candidate designs analyzed. Thus, response surface methodology(RSM)is applied in this study to optimize ship structural design. This methodology involves a few sets of mathematical techniques:the method of designing experiments to grasp efficiently the accurate features of a response with a minimal number of analyses, the least squares method to obtain an approximate mathematical expression of the response, and the nonlinear optimization method to find the optimal design, i.e., the minimum or maximum of the response. In this paper, as an example of the application of RSM to ship structural design, the optimization of transverse bulkhead structures of an oil tanker is carried out. The results obtained and the know-how accumulated in using this methodology in optimizing the structural design of ships are shown.
View full abstract
-
Mitsue MORISHITA, Shinsuke AKAGI
Article type: Article
Pages
245-253
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
In this study a variety of fast carferry concepts is examined for recently-built large fast carferries from the viewpoint of transport economy. Operating costs are estimated for three kinds of fast carferries, i.e., monohulls, catamarans and wavepiecers. After that, total transport costs are compared for several ferry routes to evaluate the transport economy competitively with each other and with other transport means, i.e., conventional carferries, land transports, air transports etc. It is found that the fast carferry has enough potential for carrying passengers and cars in several coastal routes along the Japan Islands.
View full abstract
-
Yoshiho IKEDA, Ryoichi WATANABE, Hiromi TASUMI
Article type: Article
Pages
255-265
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A new demand prediction method proposed by one of the authors is applied to domestic routes between the main land and isolated islands in Japan in this paper. To determine weights of each element in a generalized cost model for an island route, which is used in the prediction method, a survey is carried out for people in an island using AHP analysis. Using the method, feasibility studies of fast passenger car ferries in island routes are done. The results show fast passenger car ferries are highly competitive with other means of transportation in medium distance routes of 50-150km.
View full abstract
-
Ryoichi KOJIMA, Hiroyuki ADACHI
Article type: Article
Pages
267-273
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Bezaisen which was a typical Japanese wooden vessel(Wasen)having a single large sail in Edo Era is so-called Sengoku-Bune and played an active role in cargo transportation. But there were few investigations on the vessel from the technological point of view. Recently, Osaka city has reconstructed Higakikaisen which is a kind of Bezaisen. Based upon that, this paper discusses stability and sea worthiness of Bezaisen by calculating dynamic stability and motion in waves. As a result, loading capability of cargo, stability performance, probability of deck wetness etc.are clarified quantitatively.
View full abstract
-
Toshimasa SAITOH, Tomoko KITANO, Yuji HASEGAWA, Kazutaka HOSOGAYA
Article type: Article
Pages
275-280
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
To predict the behavior of a fire occurring in an accommodation area, heat conduction through the walls is an important factor for determining the room temperature and fire spread. We established a predictive method that can accurately reflect any types of wall structure(e.g.consisting of steel plate, rockwool panel and air space)and can consider the change in thermal conductivity of rockwool panel due to the variation in water content therein. This paper presents also a comparison with an experiment to demonstrate the accuracy of this method. Examples of calculating the temperature of several types of walls using this method are also shown.
View full abstract
-
Toshimasa SAITOH, Hiroshi TANO, Teruhisa ISHIHARA, Yoshirou YAMAWAKI, ...
Article type: Article
Pages
281-286
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Semi-submersible drilling rig is under the application of vibration rules during operation. The vibration limits are derived from the acceptability of the exposure of human beings to vibrations and are based on a 12-hour working day. Builder must confirm that results of estimation before building and measurement during operation are lower than vibration limits. In this paper, simplified method to estimate vibration level before building is proposed. It is based on steady-state dynamic response based on harmonic excitation and FEM. And vibration level during operation is presented.
View full abstract
-
Koji OTSUKA, Akiyoshi BANDO, Yoshitsugu MATSUMOTO, Yoshiho IKEDA
Article type: Article
Pages
287-292
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A time-domain numerical method to predict in-line dynamics of flexible risers for upwelling deep ocean water has been developed. The analysis method is based on a swing-by-swing technique with symmetrical vortices model. The effects of internal flow are considered by adding the momentum change of the internal flow, the frictional force on the inner wall of the pipe, the reduction of the internal pressure, and the reaction force of the intake flow. To validate the present dynamic analysis method, motion measurements in steady current conditions and forced oscillation conditions in still water are performed. The results in steady current conditions show that the horizontal displacement of the pipe with internal flow is larger than that without internal flow due to the reaction force of the intake flow. The results in forced oscillation conditions demonstrate that the amplitude of the motion increases when the internal flow exists.
View full abstract
-
Naoki NAKATANI, Fumi TERADA, Taketoshi OKUNO
Article type: Article
Pages
293-301
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Water quality and natural environments of the enclosed sea such as Osaka Bay in Japan, has been chronically worse by the high pollution load owing to human activities in the city. It is important for the environments to develop a management system. In order to understand the environments deeply and to propose the suitable managing system, not only measurements in detail but also numerical simulation should be made. In the present paper, the numerical simulation method of water qualities is constructed using the ecosystem model with land water effects in Yura area, where is located in the southern part of Awaji Island. This method is useful to predict the environments because these can be treated physical, chemical and biological processes. The load from land is calculated using the prediction method of run-off polluted load through river basins. The results of numerical simulation show that the load from town area is very large, but does not affect so strong to nutritive salts and phytoplankton in the coastal areas.
View full abstract
-
Toshio SUZUKI, Tetsuya TAKEMI, Teruhisa OGATA
Article type: Article
Pages
303-308
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
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 simple algorithm of measurement for water vapor content of the lower troposphere over the ocean from the 11 and 12 μm(split window)channel on the VISSR Atmospheric Sounder(VAS)on the GMS-5. A new method of measurement for ocean wind from optical flow of precipitable water distributions are described. The algorithm is applied to time series of VAS split window radiances over tropical Pacific Ocean during 17 June 1999 to 26 June 1999. The algorithm for precipitable water shows good agreement with that of radiosonde measurement. Ocean wind velocity and direction are analyzed by present method agree that of radiosonde measurements.
View full abstract
-
Toshio SUZUKI, Yasuhiro OISHI
Article type: Article
Pages
309-314
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
Recently, remote sensing technology is recognized as important way of measuring the ocean, and many sudies are done. Remote sensing by a satellite has such characteristics as mobility, a wide area and continuity, and it is necessary condition to measure the ocean. Remote sensing by a satellite is suitable for getting the average information of a large area, for example, significant wave height, average wave length, etc, but it is not suitable for measuring a wave pattern of the local area. In our laboratory, prejected light distriburion method was kept proceeding with the development of the method to measure the spatial wave height distriburion. It is generally known that the light from the bottom of tank is refracted when it passes through water surface. Projected light distribution method utilizes the principal that the light distribution projected on a screen near the wave surface has strong relationship with the wave pattern. This method, however, has two defects. One is the effects of the boundary wave heights and the other is the effect of focusing of light. This paper presents the way of improving problems on the projected light distribution method and reproducing the accurate wave height by FFT as a fundamental study.
View full abstract
-
Osamu SONODA, Hiroshige KOBAYASHI, Hideyuki SYURI, Kazutaka HOSOGAYA
Article type: Article
Pages
315-321
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
A practical method is developed for predicting the noise levels of offshore structures such as a semi-submersible drilling rig at an early design stage. This is based on the empirical method of ship noise prediction presented by J.H.Janssen. In order to estimate the noise levels of offshore structures, transmission decreases of structure borne noise through the complex structures between cabins and noise sources are represented in terms of the number of decks and girders, and the transmission path. On newly built semi-submersible drilling rig "West Venture", the noise level measurements are carried out. And the data of transmission decrease, absorption coefficient etc.are obtained in sea trial. About 62% of the calculated results is in agreement with measured results with an accuracy of ±5dB. Comparison of the calculated and measured results has validated the reliability and suitability of the proposed method. Also the vibration transmission on steel deck with damping treatment is investigated using S.E.A.(Statistical Energy Analysis)method. It has confirmed that S.E.A. method is useful to estimate transmission decrease.
View full abstract
-
Article type: Appendix
Pages
App2-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Index
Pages
Toc3-
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
55-62
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
71-78
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
149-155
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
167-172
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
-
Article type: Appendix
Pages
173-178
Published: September 25, 2000
Released on J-STAGE: April 01, 2018
CONFERENCE PROCEEDINGS
FREE ACCESS
