In various contexts of the shipbuilding industry as well as in the marine transportation industry, the relocation of objects such as steel plates, containers, etc. by using cranes is a common task. In these operations, crane operators are faced with the problem of starting with a given distribution of objects and restacking them in order to achieve a desired distribution using the least possible effort or movement of the crane. This type of problem involves a practically infinite number of solutions, since the possible combinations of operational order are so numerous. Therefore, it is difficult for the operator to determine the optimal sequence from the candidate processes, and it also is difficult to present a general method that can solve this problem with high degrees of efficiency and reliability. As a result, in practical situations the crane operators on site usually decide the sequence according to their experience and intuition. However, sometimes the planning of the crane operation process is very troublesome and time consuming and is thought to be not necessarily suitable for human beings. In this study we apply a genetic algorithm (GA) that excels at finding solutions to combinatory problems. The sequence of a crane's operation is represented in string expression and with the merit of a population search (i.e., a simultaneous multi-point search) of the GA, excellent operations were efficiently obtained for the practical examples shown in the paper.
The quantity of solid waste that is finally disposed of through production, consumption and import occupies 1/4 of the whole in material balance domestically in Japan and is approximately 500 megatons per year. In recent years, because of lack of a final disposal site, outbreak of pollution with intermediate treatment of waste disposal and social problems such as illegality abandonment, to secure a waste disposal facility has become an important problem. On account of these circumstances, the solid waste is carried from the area of disposal shortage to the other area of disposal margin of intermediate treatment facilities and final disposal sites by the wide area transportation that used a highway network. To construct the recycle based society that aimed at utilizing effectively waste as resources among different industries has become an urgent need in order to reduce the quantity of whole solid waste. For the realization of the recycle-based society, it is indispensable to build a new physical distribution system between waste discharge sources such as a consuming place and an industrial area, and waste disposal areas such as a recycling factory and a final disposal site to be dotted with individually over a wide area. From these backgrounds, a concept of physical distribution system that makes use of advantages of ship transportation in order to support the recycle-based society is proposed. And as a practical example of applying the proposal concept, the industrial waste transportation by shipping is evaluated through the calculation of CO2 emissions by conducting mathematical programming model.
The needed conditions for predicting thermal cycle of a quenching by using the finite element method have been investigated by comparing theoretical values with numerical results. The basic equation of a minimum element length for cylinder thermal cycle was proposed, which was able to calculate from informations such as an initial temperature, a radius of cylinder, a heat transfer coefficient and the aimed temperature change at the cylinder surface. The minimum time increment for guaranteeing accuracy was given against the minimum element length. It was shown that the minimum element length for pipe thermal cycle was replaced by that of cylinder. The experimental data of quenching cylinder were sufficiently predicted by the finite element method with the above minimum element length and the time increment.
In order to realize the computer simulation of twisting process of a T-shape ship longitudinal frame, the estimation technique of the temperature history within the T-shape frame during a repetitive heating is developed. Heat input during gas heating is evaluated by using the distributions of gas temperature and local heat transfer coefficient obtained in spot heating tests. These distributions are identified by the inverse heat conduction technique developed by Tomita et al. (2002). The accuracy of the heat input estimation shown by comparing the calculated and measured temperature distribution during a repetitive circular heating test. The temperature history calculated by the developed technique is used as the thermal boundary condition in the thermal-elasto-plastic F.E. calculation of the frame torsional deformation.
Temperature histories within a T-shape ship longitudinal frame during face repetitive heating and web line heating is calculated by using the distributions of gas temperature and local heat transfer coefficient identified in the previous report (Osawa N. et al, 2004). Using this temperature histories as thermal body forces, torsional deformation of frame is calculated by thermal-elasto-plastic F.E. analysis. Shell and solid F.E. models are employed in the analysis. The calculated deformation is compared with the measurement one. The calculated deformations both in shell and solid analysis agree well the measured ones. This shows the validity of the proposed thermal and deformation calculation methods.
This paper proposes a practical design system for the resistance estimation of high speed mono-hull craft. It uses regressive approach with artificial neural networks, which learn the teaching sample data of many pairs of input/output vectors, generalize it, and establish the nonlinear mapping relation between its i/o. The system consists of a tank test database, mapping neural networks, and a descriptive neural network. The tank test database is based on the Series 62 which has 1725 data records. The input of the Mapping neural networks is a set of speed, length, chine breadth, weight, and center of gravity position. While, its output is a set of residuary resistance, running trim, rise of center of gravity, and wetted surface. The descriptive neural network denotes the density of the tank test data. It indicates the designer how reliable the estimation is. The learning process of these artificial neural networks is based on back propagation method. The proposed system is easily implemented into the spreadsheet software, very easy to use, and has the practical accuracy, if the learning of the networks is once established.
In this paper we propose a Galerkin's method for the hydroelastic problem of a rectangular plate on shallow water in waves. The bi-directional complex Fourier series are adopted as a displacement function of the rectangular plate, which complex conjugates are adopted as weighting functions. The weighted residual method leads to the weak form to be solved. On the plate boundary, the weak form should be combined with Boundary Element Method. A boundary element, in which two nodes are arranged at two Gauss-Legendre integral points, is proposed to obtain the same results as 3rd order polynomial interpolation. Present Galerkin's method can calculate large ratio of plate length and incident wavelength quickly.
Generally, propeller is applied with anti-singing device for the prevention of irregular noise resulted from Karman vortices generated from the trailing edges of propeller. It is well known that the anti-singing device exercises a greater effect on propeller open characteristics (P.O.C.) and propeller shaft speed, the effect of which is to be taken into account when propeller pitch is decided accordingly. On the other hand, in the propeller open test (P.O.T.), the finished accuracy of the trailing and leading edges greatly influences test results; however, it is difficult to attain higher accuracy on the very thin trailing edges of the propeller sized 250mm, which is popularly used for the model test. As a result, the effect of the anti-singing device is frequently studied experientially without adequate accuracy in spite of a greater effect of the anti-singing device upon the P.O.C.. This paper is based on the P.O.T. using 400mm diameter model propeller, supported by such a verification procedure that the P.O.C. performance was calculated by a simple method and applied with some corrections by comparing with the model test results, followed by a consistency having been finally confirmed upon comparison with the test results on full-scale vessel.
This paper describes the design and performance of practical supercavitating propellers (SCPs). Prototypes of SCPs were designed using two design methods, in order to check both geometric forms. One was developed by SSPA, and the other was based on the theoretical research having been advanced in recent years. The differences were shown about the blade contours and the blade section distributions. Moreover, prototypes of SCPs were designed using the theoretical design method on several design points corresponding to the practical use range. Then, the series of standard geometric form for practical SCP model was determined based on the geometric form acquired by these prototype designs. Using the theoretical design method and this series, two models of SCPs were designed, manufactured, and tested in a large cavitation tunnel at the National Maritime Research Institute. As the result, the performance of the practical SCP model was shown to be equivalent or better than that of the theoretically designed SCP.
In high speed planing, the scale of free surface deformation and extended spray become comparable to the ship length. In numerical approaches of the problem, some difficulties arise from the mesh generation around the large, irregular formation of the free surface. One of its alternative approaches is the particle based computational fluid dynamics. The present authors applied the Moving Particle Semi-implicit (MPS) method originally developed by Koshizuka1) to the problem of high-speed planing. This paper describes the modifications to the MPS method to solve the problem, and shows numerical results of spray formation around a wedged cylindrical model.
The oar blade acts as unsteady hydrofoil in stroke phase. The authors1) carried out a tank test using a flat plate in the place of an oar blade in order to quantitively analyze the unsteady load acting on an oar brade. This time they carried out the same tank test but they used four kinds of real blade shape which have different aspect ratio or tip shape (Original- blade, High aspect ratio, Low aspect ratio, and Delta-blade). And they study the influence of aspect ratio and tip shape on the load acting on an oar blade.
It is a great concerning problem for a mariner to know how maneuvering method is the best for his ship. Moreover it is also important for a ship builder in the meaning how the designed ship shows the maneuvering performance in full conditions. A minimum time maneuvering yields an answer about this problem. The minimum time maneuvering problem of ship can be formulated as two point boundary problem. The author has solved this non linear problem using the Sequential Conjugate Gradient-Restoration Algorithm (SCGRA) by Wu and Miel. This numerical method was a powerful solving method. However, a tedious programming method was needed. In this paper, the author proposes to treat this problem in a non linear programming formulation. According to this, our problem is transformed to more easy one and we can solve the transformed one by using a general Non Linear Programming (NLP) package. In this paper, the author solves a minimum time changing course problem and a Williamson's turning (man over board) one which are described by non linear mathematical maneuvering model.
The coast in Japan has been often attacked by the typhoon. And then, structures that have been installed there have been hit high waves and strong winds. Especially, for floating structures, safety measures with these high waves and strong winds have been most important subject for their design. In the case of a kind of floating structure positioning by slack mooring system using mooring lines, it has been at risk for breaking of mooring lines by slow drift oscillations contributed non-linear long period fluctuating wave drift forces. Therefore, it has been necessary to evaluate the slow drift oscillation in design process of a floating structure. However, it seems that the evaluation has been not fully carried out, for paucity of the data with slow drift oscillations on open sea test site, and for complexity of calculation method due to non-linearity of slow drift oscillations. So, in this paper, a practical estimation method with slow drift oscillation amplitude has been presented. And this estimation method has been examined for its validity based on the results of open sea tests of an offshore floating wave device“Mighty Whale”. Additionally, coefficients being used in this presented method have been examined.
Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been engaged in research and development of ocean-wave energy extraction technology for many years now. In particular, work began in 1987 an offshore floating type wave power device called “Mighty Whale”. Theoretical investigations and model tests led to an understanding of the hydrodynamic behavior of device, and provided information of constructing for the prototype of Mighty Whale. The open sea tests were started on the 10th of September 1998. Tests were conducted until March 2002. In this paper, firstly, the characteristics of hydrodynamics with “Mighty Whale” have been examined comparing with the results of experiments and calculations approving a numerical method being developed. Secondly, using developed numerical analyze method, the displacements of water level inside air chambers of “Mighty Whale” have been calculated. The generating outputs of “Mighty Whale” have been estimated using these results, the efficiency of primary conversion and the efficiency of secondary conversion of “Mighty Whale” getting through the experiments that had been carried out.
A time-domain computation method based on the hybrid method is originally developed and applied to the wave-making problems of ships both in the carm water and in waves. The fluid domain is decomposed into the near field and the far field, and the space-fixed artificial surface like side-walls of a towing tank is employed to separate them. The Rankine panel method and the Green function method are applied to two domains respectively and the solutions in both domains are combined on the artificial surface. The former makes the present method flexible to the free-surface condition and later guarantees the radiation condition for any frequency. The use of the space-fixed artificial surface makes the theory free from the line-integral which usually appears along the intersection between the free-surface and the artificial surface when the moving artificial surface is used. The method is applied to the steady and the unsteady wave-making problems of the modified Wigley model, Series-60 (CB=0.6) and Series-60 (Cb=0.8). Through the comparison of hydrodynamic forces between computed and measured, it is confirmed that the present method is very accurate and rational for any case.
A time-domain hybrid method developed by authors is applied to estimate the unsteady wave field of ships advancing in waves. The method is combining the Rankine panel method applied in the near field and the Green function method applied in the far field of ships, and it makes possible to satisfy the radiation condition exactly at least from theoretical point of view. The method is, therefore, the mostly expected among many numerical methods to be reliable on the satisfaction of the radiation condition even in the low-frequency region where the κ2 wave system propagates upstream of ships. The wave elevation is used as a typical physical-value which represents the wave field around ships. The computed wave elevation by the present method is compared with experimental results and with another numerical result by the Rankine panel method. Through the comparison, it is confirmed that the present hybrid method can estimate the wave elevation with high accuracy and applicable to the low-frequency region without losing accuracy.
The purpose of this study is to investigate the effect of pitting corrosion on local strength of hold frames of bulk carriers. In the present study, a series of 4-point bend tests with structural models which consist of web, shell and face plates has been conducted. Artificial pitting was made on the web plate. In these tests, two equal concentrated loads has been applied at the one third points of simply supported models so that compression load would act on the face plate. In this testing condition, lateral-distortional buckling occurred before ultimate load was reached and local buckling of the face plate was observed after the ultimate load. It has been revealed that the effect of pitting on the web plate on lateral-distortional buckling load was small but ultimate load decreases with the increase of area ratio of pitting. As a result of FE-Analysis, the ultimate load of the structural models where pitting prevailed uniformly on the web plates was found to be almost the same as that of the structural models where the web plates have uniform corrosion corresponding to the average thickness loss.
The objective of this study is to investigate the effect of pitting corrosion on local strength of hold frames of bulk carriers. In the present study, a series of 3-point bend tests with structural models which consist of web, shell and face plates has been conducted. Artificial pitting was made on the web plate. In these tests, a concentrated load has been applied at the center of simply supported models so that compression load would act on the face plate. In this testing condition, local buckling occurred just after ultimate load was reached. It has been revealed that ultimate load decreases with the increase of area ratio of pitting. As a result of FE-Analysis, the ultimate load of the structural models where pitting prevailed uniformly on the web plates was found to be almost the same as that of the structural models where the web plates have uniform corrosion corresponding to the average thickness loss.
The steel water gate, which received variable water pressure due to gap of water level between sea and balancing reservoir, damaged in its gate lip by fatigue crack. As the measures, the damaged part was replaced with new stiff elements, and various investigate programs, including observation with microscope and measurement of stress and water level, were performed. This damage was caused by the unneutral loading on the gate lip from the ground surface. The crack growth estimation was executed with FLARP, and it is confirmed that the possibility reoccurrence of fatigue crack was removed by the measures which we had taken.
At first, based on the recognition that fatigue limitt is the condition including many stationary cracks with 'cusp' shape at maximum load, crack opening/closing phenomena and stress distribution near the crack tip is considered. Then, it is mentioned that alternate appearance of compressive plastic zone and tensile plastic zone is necessary for crack propagation under cyclic loading. And, because the crack extension timing has not explained yet and influences the crack opening/closing phenomena, we should consider this unresolved problem when we carry out the crack propagation simulation. Finally, it is indicated that, even if under the fatigue limit, we can not ignore the possibility of 'propagation of stationary crack' when a loading amplitude grows up to larger one.
The authors proposed a set of closed-form simple formulae to estimate ultimate strength of a continuous stiffened plate under combined longitudinal thrust, parallel to stiffener direction, and lateral pressure. This paper extends the application of the formulae to biaxial thrust condition based on a series of elastoplastic large deflection FE analyses. It was found from FEA that the ultimate strength of a continuous stiffened plate under transverse thrust is significantly higher than that of a continuous unstiffened plate simply-supported along stiffener lines because of a stiffener's torsional stiffness. It was also found that there exist two fundamental failure modes; one is local failure mode of plate between stiffener under predominantly transverse thrust and the other is over-all failure mode of stiffened plate under predominantly longitudinal thrust, and that the ultimate strengths corresponding to the respective failure modes can be estimated rather independently, with little interactions. Based on these observations, a set of simple ultimate strength formulae has been derived, and their validity has been confirmed through a comparison with FEA results.
Corrosion of structural members of ships is one of the main problems for ship safety. In this report effect of grooving on static strength of corroded fillet welded joints for ship structure is investigated with experimental result and FEM analysis. Four points bending test was conducted with half size model specimen of hold frame of Cape-size bulk carrier. It is mainly obtained that in case of grooving in compressive stress region applied by bending moment, at fillet welded joint, maximum load occurs at lateral deflection of web plate and grooving width and grooving depth effects maximum load. When the size of compressive stress region is small at grooving part of fillet welded joint effect of grooving on static strength is not observed.
Many researches for a Semi-submersible Type Megafloat have been done on the middle-scale floating airport. However, few researches have been done from the viewpoint of the design of an elastic response. A characteristic of the elastic response must be designed under the constraints that a structural response is small enough and a safety of the structure is guaranteed. This is a subject to be investigated further. In this paper, in order to find the optimal form of a semi-submersible type megafloat, efficient optimization procedure is proposed. An objective function based on a concept of a risk is proposed in this optimization. This function unifies the structural weight and requirements of strength and functionality of the Megafloat such as a motion and an elastic response. To reduce heavy burden of calculation, a simplified analysis model with sufficient precision and short calculation time was developed and used for the optimization. The simplified analysis model was consisted of the equation of motion of a rectangular plate. Using this model, the value of the objective function was optimized and more efficient form of a semi-submersible type megafloat could be obtained.