This paper describes recently developed general-purpose optimization system, in which users are able to set up the optimization problem without knowledge of system coding. Currently two optimization algorithms are implemented, i.e., the sequential quadratic programming (SQP) and the genetic algorithm (GA), both of which are the most widely used nonlinear programming techniques. The distributed-object technique, i.e., CORBA, is implemented in the present system for remote networking computation, which enables the network distributed processing to evaluate objective and the constraint functions at different computer sites. Users can set up variety of optimization problems by using spreadsheet screen.
For demonstration of the present system, two design optimization problems for container ship are considered, i.e., minimization of annual fuel consumption, and maximization of annual gross margin. Results from two optimization algorithms, i.e., SQP and GA are compared for the computational performance. Also, computational time is compared among three methods to evaluate objective and constraint functions, i.e., method using EXE and DLL files and CORBA protocol. In conclusion, the present system has been shown very promising, and can be a practical and useful design tool through further extension for CAD and CFD interfaces, which is currently in progress.

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An apparatus of exciting a wave-suppressor plate usually equipped at outlet top of a circulating water channel (CWC) in heave and pitch motion is devised for making a progressive wave system with only one wave length on the water surface of a uniform flow in the CWC in order to conduct ship model performance test in waves. As well known an oscillating body in a uniform flow makes generally four progressive wave systems or two systems, the wave number being α₁ (following wave) and α₂ (head wave), in usual test conditions for model ships. At first a numerical simulation is performed by applying the two-dimensional linear theory of an oscillating planing plate to confirm possibility of making α₁-wave disappear and of generating α₂-wave only and to obtain α₁-wave-free condition of combination of heaving and pitching of the wave-suppressor-plate. Next, experiments are conducted in a small CWC after developing a method of separating α₁- and α₂-components from the measured envelop of beating waves generated by the oscillating suppressor-plate. Through some iterations of a process of getting α₁-wave-free condition of oscillation combination of the wave-suppressor-plate from the two experiments of different combinations, wave fields consisting of only α₂-wave are obtained for three frequencies (3,4 and 5Hz) and two amplitudes at three velocities (0.5∼1.0m/s). Though these α₁-wave-free results do not correspond very well with the simulations mainly due to the non-linearity of the real motion of the wave-suppressor-plate, it is concluded that more accumulation of experimental data makes this type of wave maker generate any progressive wave system with single wave length in CWC.

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Recently, the simulation technology by CFD (Computational Fluid Dynamics) has made remarkable progress. The method has become to be applied to viscous flow problems around not only various ship hulls but also marine propellers. Consequently many difficult problems on flow analysis on account of remarkable viscous effect are being resolved. There are also many subjects related to viscous effect of the flow around marine propellers. In this paper the author presents the topics about hub vortex and scale effect of propeller performance characteristics. The used analytical method consists of commercial CFD software and multifunctional grid generation software. As a result, the structure of flow around hub vortex and the difference of scale effect due to propeller shapes were revealed. These results show that the method is useful for design of such energy-saving devices as PBCF (Propeller Boss Cap Fins) or Kawasaki RBS-F (Rudder Bulb System with Fins), for ship power estimation with higher accuracy and for improvement of propellers performance.

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The present paper investigates the shallow water effect on the hydrodynamic characteristics of lifting body such as wave resistance, sinkage and trim using a potential based boundary element method. The surfaces are discretized into flat quadrilateral elements and the influence coefficients are calculated by Morino’s analytical formula. The body boundary condition is linearized about the undisturbed position of the body and the free surface condition is linearized about the mean water surface by the systematic method of perturbation. The results of investigation provide a better understanding the effect of hull separation on the wave resistance of catamaran hull. The influence of water depth on trimaran is, in principle, the same as the influence of water depth on mono hull in the sense that the same type of subcritical, critical and supercritical region is recognized. The peak of wave resistance curve and wave pattern at the critical speed check the validity of the computer scheme.

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In order to develop a resistance test method for high speed planing craft using a very small model, the scale effects on wetted surface area, frictional resistance and pressure forces acting on a small model are experimentally investigated using geometric similar prismatic planing surface models. Froude number and Reynolds number covered in the experiments are Fn=1.0∼4.0 and Rn=5 × 10⁵∼3 × 10⁶, respectively. Through the analysis of resistance components, it is found that a resistance component created by disappear of hydrostatic pressure on the transom due to high-speed, called transom pressure resistance in the paper, plays an important role in the resistance of a planing craft. The wetted surface area is confirmed to slightly decrease for a very small model at large trim angle, and to cause the reduction of the pressure force acting on the hull. The frictional resistance acting on a very small model can be predicted on the basis of the equivalent flat plate concept if appropriate prediction formulas, in which laminar and transient flow effects are taken into account, are used.

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As well known, propeller and hull of ship are fouled and their surface are roughened due to various causes such as adhesion of sea-lives, painting degradation, cavitation erosion etc. The surface roughness induces so not only the crease of hull frictional resistance, but also the deterioration of propeller performance gets worse undesirably.
This paper investigates the influence of surface roughness on propeller performance. A series of experiments are carried out in order to investigate how the propeller performance is affected by its surface roughness using a model propeller of which blade surface has been roughened artificially.
A numerical estimation method of roughness effects on propeller performance is developed by the use of a model that the propeller blade section is deformed apparently by the boundary layer displacement thickness. The validity of this method is confirmed by the comparison of experimental results. Further this method is applied for estimating the fouling effect of an actual propeller of the training ship “FUKAE-MARU” of Kobe University of Mercantile Marine.

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Measurements of the velocity-pressure correlations, double- and triple-velocity correlations called the pressure-diffusion, Reynolds stress and the turbulent transport, respectively, in the self-preserving circular turbulent jet were carried out in the water tank in order to evaluate the magnitude and the structure of the turbulent diffusion terms. The velocity and the pressure in the jet were simultaneously measured by an X-type hot film sensor and a pressure transducer with a fine static pressure tube respectively. Measured data show that the structure of the turbulent transport in the circular turbulent jet is similar to the structure modeled by differentiating the Reynolds stress called the gradient diffusion model when the pressure-diffusion is unrelated, however, the structure of the pressure-diffusion and the turbulent transport are different from the gradient diffusion model when these terms should be modeled together. The problems and possibility of the modeling of the pressure-diffusion term are discussed using measured data.

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The characteristics of a plunger absorbing wavemaker are studied. In the present wave absorption system the wavemaker is controlled to absorb the incoming waves by means of digital filtering of wave elevation signal measured in front of a wavemaker. This study is focused on the influence of plunger’s shape on wave absorption. Instead of the wedge-shaped plunger whose performance was investigated before, the plunger with the cross section having a plumb part near the free surface is adopted as the wavemaker. The absorption efficiency is investigated in period 0.5sec to 1.3sec.

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In this study, critical wind velocity of a Ro-Ro passenger ship equipped with side thrusters are examined. Two different methods were developed to identify the critical wind velocity. One is based on static equilibrium. The other is numerical maneuvering simulation of the ship in a port. Wind forces and moment were compared with forces and moment acting on a ship caused by side thrusters or rudder angle. Furthermore numerical maneuvering simulation in a port was also developed to confirm the calculation results. This paper may offer a more efficient way to estimate critical wind velocity of a ship equipped with side thrusters in a certain port.

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This paper describes the hydrodynamic forces acting on a ship hull undergoing lateral berthing maneuver. The hydrodynamic forces acting on the ship hull shows quite complicate and transitional characteristics due to the complex flow field around a ship and has a deep relation to the strength and position of vortices. In order to understand the phenomena for berthing problems, a numerical calculation for time-domain simulation using 3D CFD technique was employed for basic consideration of the hydrodynamic forces especially to estimate the drag force acting on a Wigley model moving laterally from rest in deep water. The numerical solutions successfully captured not only the characteristics of the transitional hydrodynamic forces but also some interesting features of the transient flow. The computational results of the hydrodynamic forces were in good agreement with experimental results.

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Maneuvering motions of fishing vessels are important in the situation of fishing operation at slow ship speed. Especially the roll motion of the fishing vessel relates to the capsizing by steering motion in the situation of small metacenter height GM due to lifted net full of fishes on deck and the movable net lifted by winch ropes. This paper deals with the surge, sway, yaw and roll motions of two steered fishing vessels, which are simulated by the component-type mathematical model¹⁾ of ship hull hydrodynamic forces for the North European fishing vessel L/B=2.6 and the Japanese fishing vessel L/B=4.6.
By comparing the results of free running measurements with the numerical simulations based on captive model tests for hydrodynamic forces acting on the hulls, it is found that the component-type mathematical model can estimate the maneuvering motion with roll and running trim precisely.

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In the dynamic positioning control and thrust allocation system of the vessels, it is difficult to obtain an optimal solution in real time because of inherent non-linearity, and development of a reliable real-time calculation method for the optimal control has been waited for. The control system we have developed realizes a real-time optimal control. This paper presents examples of application of the real-time nonlinear receding horizon (RH) control for route-tracking and real-time algorithm for optimal thrust allocation for redundant actuators. The effectiveness of the method applied to the systems is verified by computer simulation and experimental study conducted at a model test basin.

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The Core-University Scientific Corporation Program has started between Philippines and Japan from 1998. The project of fishing craft is conducted to improve the performance of Philippine outrigger craft. Most fishing craft of the Philippines are constructed in the double outrigger form with a main hull and floats at both sides. Generally, a float and its beam are made of bamboo.
In this paper, the characteristics of ship motions are experimentally investigated to clarify dangerous sea conditions for the craft in waves. A computer program has been developed to calculate ship motions of the craft. The accuracy of this computer program is checked by measurement of ship motions in waves. Furthermore, results of the calculation are in good agreement with the measured ones. From these results, the outriggers increase heaving and pitching motions in head seas at the short wave length, although significantly decrease heaving and rolling motions in beam seas.

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The Core-University Scientific Corporation Program has started between Philippines and Japan from 1998. The project of fishing craft is conducted to improve the performance of Philippine outrigger craft. Most fishing craft of the Philippines are constructed in the double outrigger form with a main hull and floats at both sides. Generally, a float and its beam are made of bamboo.
In this paper, a prediction method of the maneuverability for the craft is proposed to investigate the maneuvering motions. The point about the development of this method is divided into different parts of the hull and the outriggers. Furthermore, the model of hydrodynamics forces on outriggers is described as a simple mathematical formula. The accuracy of the method is checked by model tests. From these simulation studies, a safer and more efficient craft could be designed.

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Serious capsizing accidents have occurred mainly with purse seiners among other fishing vessels in Japan. Therefore, it is one of the most important tasks to prevent accidents of the purse seiner. Capsizing model experiments were carried out to identity dangerous scenarios. The models of 135GT, 80GT and 39GT purse seiners of Japan were used for these experiments. These models were capsized by broaching-to, pure loss of stability and bow diving. It is noteworthy also that North European purse seiners have quite different hull forms from Japanese ones. To establish international stability criteria applicable to both vessels, it is important to compare North European and Japanese purse seiners. Thus we conducted the capsizing model experiment of North European purse seiner as well, and observed that the model capsized by pure loss of stability, broaching-to and subharmonic rolling. Capsizing mode of subharmonic rolling here is different from low cycle resonance or parametric resonance. While, the roll period of low cycle resonance is equal to the natural roll period, the periods of subharmonic rolling were two times as long as the encounter wave periods and not relevant to the natural roll period. These qualitative differences between North European and Japanese purse seiners should be taken into account in establishing internationally applicable criteria.

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Stochastic process models of significant wave height and standard deviation of ship responses are proposed based on the Langevin equation which is a kind of stochastic differential equations. The probability density functions of their variables are obtained as the solution of the Fokker-Planck equation related to the Langevin equation. In addition, the detail of the proposed stochastic models in large wave height is discussed from the view point of the wave breaking theory. For the model construction and the evaluation of the model validity, time series data measured in the actual sea are used.

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Vibration guideline for passenger and merchant ships (ISO6954) was revised at the end of 2000. The main aim of this revision is to establish compatibility with vibration standard of whole body vibration of human body. (ISO2631-1-1997) In this paper, the transition and features of ISO2631 was introduced at first. Correlation of vibration standard between human body and ships were discussed. A method to represent sensitivity curve was proposed as functions of frequency-weighting curve and vibration severity value. A general mathematical expression for sensitivity curve with folded straight lines and frequency-weighting functions having product of hyperbolas was derived. It became possible to compare vibration standards for different evaluation methods. Some examples of comparison between different ISO standards were discussed.

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A large number of cruciform joints can be found in ship structures, but it is generally known that it is not clear how FEM stress output ought to be used and how FEM input ought to be prepared for fatigue strength estimation of welded structures with cruciform joints. In this study, a consideration was made on FEM modeling, and eventually it is made clear that the shell (plate) element FEM may overestimate the stress concentration factor at the cruciform joints applied bending moment. And it is found that the hot spot stress by FEM can be used in order to assess the fatigue strength of cruciform joints on the basis of its practicality. As the result of these studies, the practical evaluation method of stresses around cruciform joints is established.

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The welding distortion of a plate structure during the assembly process is influenced not only by the local shrinkage due to the welding thermal cycle but also by the root gap and the misalignment. The former is governed by the heat input. Meanwhile, the latter is strongly affected by the welding procedure, such as the welding sequence and restraint on the joint to be welded. In this research, a method to predict the precision of plate structures during assembly process considering these factors is developed. The proposed method employs the concept of inherent strain and the interface element to consider both the local shrinkage due to welding and the gap and the misalignment in weld joint. The proposed method is applied to study the influence of welding sequence on the distortion of the structure during assembly by welding.

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This paper addresses an quantitative procedures in decision-making process to determine whether marine machinery that have been entering the wear-out phase need to be replaced, or only demand preventive maintenance action. Components must be replaced if they cannot attain the minimum requirement of reliability index (RI) and availability index (AI). In the case when the preventive maintenance is the decision to be taken, this paper also recommends the optimum interval between maintenance based upon the minimum total cost (the objective function) rendered by the decision. An assumption is taken in which onboard maintenance is not possible; hence penalty cost are induced until the components are repaired in yard/port and become operable. Premium Solver Platform (PSP), a spreadsheet modeling tool, is utilized to model the optimization problem. Constraints, which are considerations to be fulfilled, become the director of this process, and a minimum and a maximum value are set on it to give the working area of the optimization process. The model takes a finite and n-equal interval between maintenance, and the increase of operational cost and maintenance cost due to deterioration is taken into account. An analysis on main engine cooling pumps of a ship is adopted as the case study.

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The authors have proposed a 20 feet container size electric Package Generator Unit (we call this unit PGU hereinafter) which is integrated with a 800kw electric generator, coupled with a 900rpm diesel engine. The newly introduced marine machinery plant consists of many PGUs that cover both power sources of propulsion and onboard electric services. Thus, this new plant aims at higher reliability of ship’s propulsion system having redundancy by providing spare PGU(s) on one hand, and un-manned engine room by maintenance free on board on the other. This paper introduces the above concept that adopts a container ship as model ship.

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O’Hanlon et al. gave a full rage data on motion sickness for single frequency sinusoidal vertical motions. When it is used for ship motion, there are some problems because ship motion distributes in wide frequency range. In this paper, motion sickness in two frequency vertical motions and ship motions distributed in wide frequency rage are studied. And it is shown that vertical acceleration components in higher frequency range may have bigger effects on motion sickness than estimated from O’Hanlon’s data

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The study is of an offshore structure consisting of slender columns near the free surface and large buoyancy pontoons near the base that is moored to the sea bottom like a Tension Leg Platform. The effect of the spacing between the columns of the structure on the horizontal component of the total wave force due to an irregular wave has been investigated. Since the columns are slender, diffraction of the incident wave field has been neglected and the wave force has been computed using a method proposed by Borgman for an irregular wave. This research has been done to get an insight into the design of an offshore structure that will experience low horizontal force. The sea state¹⁾ considered is one having a significant wave height of 6m and a mean wave period of 6s since the probability of exceedance of this sea state is low in the west coast of India where the use of this structure is contemplated. The research presented in this paper is an extension to the research published by the author²⁾ in the Journal of the Kansai Society of Naval Architects, Japan in September, 2001. The research paper of September, 2001 dealt with the wave force and the consequent optimum arrangement without considering the motion of the structure. In the present research, the motion of the structure has been considered and the wave force and the optimum spacing has been determined in this context.

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This paper deals with the effects of tidal currents on the weather routing for a small vessel in a narrow sea area. The computer simulation of the sailing based on the tidal simulation is carried out for the purpose of the optimum routing concerning the shortest navigation time for a small vessel. Also, the experiments of the sailing for an actual small vessel in the same sea area are carried out for the purpose of the examination of simulated results of current sailing.
The experimental data are compared with the results of current sailing simulation. Both results are very similar. As for the results, it was considered that the effects of tidal currents for ship sailing were very important for considering the optimum current sailing on a short navigation time. It was recognized that the tidal simulation for the weather routing of a small vessel was very effective.

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In the present study, a new prediction method of travel demand of cruise ships is proposed in which the characteristic of each demand for choosing a tour, the characteristics of tours, and factors of expense, time, seasickness, and popularity are taken into account. In the method, firstly, potential share of each tour, which is hot spring, cruising, theme park, and traveling abroad, is determined based on age and gender by using the characteristic of each demand for choosing a tour and the characteristics of tours. The characteristic of each demand for choosing a tour is analyzed by determining weights of nine elements, which are communication, relaxing, resting, nature, feeling of free, knowledge, curiosity, luxuriant and thrilling, based on taste and behavior of each demand by using the Analytical Hierarchy Process (AHP) model from survey data of general people who want to travel. The characteristics of the tours are analyzed by determining their weights for the nine elements by using AHP model from survey data of professional people who properly understand about all the tours. Then, using the predicted potential share for cruising, the number of demand of cruising is determined by using distributions of travel demand for traveling expenses and days, and factors of seasickness and popularity. Using the predicted number of demand, an economical analysis is carried out to determine the optimum fleets based on economic margin ratio and business impact. This method is applied to the Japanese cruise market and the results are discussed.

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A seaquake generation tank was constructed, in order to verify the validity of the numerical calculation method of seaquake. For the first step of the study, the seismic wave field and pressure distribution in the tank are measured, in order to make clear the characteristic of compression waves in the tank. The measured results will be compared with the calculated results by making use of the boundary integral equation method.

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This paper shows the result of analysis using a number of data which have been investigated by the Osaka-Prefectural Fisheries Experimental Station for long years. The temporal and spatial characteristics of the environment of Osaka Bay are clarified by multivariate analysis technique. The results show that phytoplankton and nutrient are principally important of course, and the features of the water quality are different depending on location. The seasonal change is also shown that the phytoplankton increases from spring to autumn, and nutrient increases from autumn to winter. The degree of the seasonal change in the recesses of the bay is very larger than that in the mouth of the bay. Furthermore, the results of water density clarify the spatial-temporal characteristic of water body in Osaka bay.

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In order to manage and assess coastal environment, developing of a monitoring system is becoming important and urgent theme recently. The authors emphasize that the monitoring system should include not only measuring and watching but also short-term prediction and assessment of environmental factors. The measuring techniques by using images of the sea surface have been developed and a new assimilation technique has also been proposed for Yura area in the previous paper. This paper deals with the monitoring method of phytoplankton by the assimilation, in which a simple mathematical model and the measured data are used effectively. The present method is explained in general form and examined in detail. The effectiveness of the method is shown by the field measurement at Yura.

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Some of the environmental factors such as dissolved oxygen, chlorophyll, turbidity and so on can be measured by electric sensor recently. It enables to measure these continually and automatically. This kind measurement is very important for monitoring of the environment of coastal area. However, since it is difficult to measure the chemical parameter continuously because of its reaction time, the so-called batch type analysis has to be employed. In order to monitor the nutrient in ocean, the measurement of dissolved nitrogen is most important because it is useful for understanding a particular behavior of the phytoplankton as the primary production. In this paper, the method of absorption rate measurement of processed water by the visible ray is described. The water is drawn through pipe by a tube pump and processed with a reagent. After the chemical reaction through mixing coil, the absorption rate is measured by electric sensor continuously. The effectiveness of the present method is shown in the field measurement in Osaka Bay.

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A model to estimate and compare the economical feasibility and the ecological impact of the marine transportation (cargo ships) and land transportation (trucks) in monetary values is presented in this paper. Life cycle inventory analysis, required freight rate and the service time were used to evaluate and compare the ecological impact and find the economical superiority. The estimation was made for nine different routes in Japan. Finally the social cost saving in monetary value through the modal shift of cargo from trucks to cargo ships is presented.

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