"SEA-Arrow", developed by Kawasaki Shipbuilding Corporation, is an advanced new bow form for medium-speed ships such as LPG carriers. The bow end form of SEA-Arrow around the loaded draught is much sharper than that of conventional hull ships. With SEA-Arrow, bow waves are greatly reduced in loaded condition compared with conventional hull ships. Model tank test results show that SEA-Arrow can reduce the wave resistance to a half and the required main engine horsepower by 6-10%. On the other hand, the superiority of SEA-Arrow ships' propulsive performance in loaded condition cannot be verified in sea trial because actual ships' speed tests in sea trials are generally carried out in ballast condition except oil tankers. Therefore, the authors have analyzed, to confirm the high propulsive performance of SEA-Arrow ships, the voyage data of three SEA-Arrow ships and one conventional hull ship, which are sister ships of 59,200m3 LPG carriers. The results show that the propulsive performance of the SEA-Arrow ships is superior to that of the conventional hull ship and that its analyzed speed advantage agrees with the estimate from the model tank test results.
The authors developed a component-type mathematical model of hydrodynamic forces acting on a ship hull in steering motion and the availability of the model have been confirmed by experimental data. The mathematical model describes longitudinal force X, lateral force Y and yaw moment N for ship motion with 3 degrees of freedom, and it can cover a wide range motion with small to large yaw rate and drift angle. In this paper, we describes a component-type mathematical model of heel moment K composed of lateral force components for ship motion with 4 degrees of freedom. By the model, heel moment can be estimated easily with known hydrodynamic characteristics analyzed from the hydrodynamic forces X, Y and N.
In the present study, measurements of running attitude (; rise, trim angle and heel angle) and three-components of hydrodynamic forces (; drag force, sway force and yaw moment) are carried out for planing boat models by an obliquely towing test. The ratios of length to breadth of the models are 6.0, 4.5 and 3.0 respectively, and they are more slender than the high-speed planing craft models which were tested in previous works. The range of Froude-number in the present experiments is from 0.3 to 1.8. The measured results demonstrate that the heel angle is drastically changed by the drift angle, the forward speed and the ratio of length to breadth. The change in the running attitude causes significant effects on yaw moment acting on the models. It is also found that the rise and trim angle of the models are significantly affected by the drift angle. The results suggest that it is necessary for predicting maneuverability of planing craft to take the effects of the running attitude on the hydrodynamic coefficients in maneuvering motion equations into consideration.
Roll motion of a two-dimensional model of the center part of a damaged large passenger ship is measured from the start of flooding to the end of flooding in calm water. The experimental results suggest that large roll motion sometimes occurs in the intermediate stages of flooding although the ship is safe at the end of flooding. The behavior of ship motion in the intermediate stages of flooding is significantly complex, and depends on many factors, for examples, air ventilation though bulkhead deck, GM, location and size of damage openings, detailed arrangement on decks and so on. It is confirmed that the maximum roll angle in the stages can be approximately predicted by quasi-static stability calculation. When the superstructure of a damaged ship is damaged and water flows into the bulkhead-deck, capsizing is observed in the experiments. This fact suggests that prevention of spreading water on the bulkhead-deck is very important for the safety of such a large passenger ship in the intermediate stages of flooding after damage.
The water entry problems of a wedge with vertically constant velocity are studied by using the boundary element method. The computational models about jet flow are proposed. These are applicable to the problems for wedges with various dead rise angles and additionally make it possible to simulate the free surface evolution in the jet flow region. In predicting the pressure on the wedge, it turned out that the singularities at a bottom apex were apt to lose computational precision. Accordingly we introduce the analytical description of solutions in the local domain around the apex. We can obtain the analytical solutions matched with the numerical solutions in the other domain.
This paper discusses guidance and control of an underwater robot equipped with 2 pairs of the mechanical pectoral fins by carrying out two kinds of the tank experiments in still water and in water currents. Fuzzy algorithms were used in the guidance and control. The first kind of the experiment was to guide the underwater robot from a far point to an underwater post by controlling the position both in the vertical plane and in the horizontal plane. In still water, the underwater robot was firstly guided to a waypoint located in the elongated longitudinal plane of the underwater post and was next guided to an underwater post. In water currents crossing the course of the underwater robot, the underwater robot was guided to the first waypoint located upstream from the longitudinal plane of the underwater post, and was next guided to the second waypoint located in the neighborhood of the underwater post by making the underwater robot drift downstream, and was finally guided to the underwater post. The second kind of the experiment was to guide the underwater robot around the surface of a circular cylinder by keeping the distance between the surface of the circular cylinder and the underwater robot constant and directing the head of the underwater robot to the center of the cylinder. In still water, lateral swimming control, distance control between the surface of the circular cylinder and the underwater robot, and azimuth control to direct the head of the underwater robot to the center of the cylinder were simultaneously performed by allotting the lateral swimming control to the fore mechanical pectoral fins and the distance control and the azimuth control to aft mechanical pectoral fins. In water currents, the underwater robot was firstly guided from an upstream start point to a downstream waypoint by making the underwater robot drift downstream along the water currents under the control of the azimuth control and the distance control, and was next guided from the downstream waypoint to the upstream start point by taking a roundabout course.
We are anxious about the occurrence of Tokai, To-Nankai and Nankai earthquake. Tsunami attack generates not only the raise of sea surface but strong horizontal current in the bay It is very important for marine disaster prevention to grasp the drifting motion of a vessel caused by the tsunami curent. From such viewpoints, a basic analysis method for ship drifting phenomena by tsunami attack was developed. According to the ship drifting simulation by tsunami at the bay of Owase, Mie Prefecture, we found a possibility that a vessel collides with a berth, and also a possibility of ship grounding by the tsunami current. Such results suggest that still more detailed examination is required in the future.
The ultimate longitudinal strength of hull girder is, in usual, analyzed for the cross-section where the maximum longitudinal bending moment occurs. In this case, the effect of shear stress is not considered, since the shear force is zero at this cross-section. There exists, however, the cross-section having large bending moment together with large shear force for example in case of an alternate loading condition of bulk carriers. For these cases the ultimate hull girder strength analysis taking the effect of shear force is expected. This paper introduces, at first, the method to calculate the shear stress distribution and warping deformation of the hull girder cross-section loaded by shear force. Using this result, the progressive collapse analysis by "HULLST" was carried out to estimate the ultimate longitudinal strength of hull girder cross section taking the effect of shear force into consideration.
Since welding is a transient and highly nonlinear mechanical problem, large computational time is required to solve by the finite element method. To improve the speed of computation, the authors developed an iterative substructure method which takes advantage of the characteristics of the welding problem. Noting the fact that the region which exhibits strong nonlinearity is limited in a very small area compared to the size of the model to be analyzed and the remaining part is linear, the problem is transformed into the combination of a large linear problem and a small but moving nonlinear problem. The continuity on the boundary between the linear and the nonlinear regions are maintained through iterative procedure. The effectiveness of the proposed iterative substructure method is demonstrated through a numerical example.
Inherent deformation method, in which the inherent deformation is introduced into the elastic FEM as the initial strain, is one of the effective methods to predict welding deformation of large structures, such as ships, bridges and automobiles. When the welding length is long enough, the inherent deformations namely, longitudinal shrinkage, transverse shrinkage and angular distortion are mainly governed by the heat input Q and the thickness of plate h. When the welding length is short, the inherent deformations are also influenced by the length of weld. In order to estimate inherent deformations for short welding, an efficient measuring method to obtain inherent deformation of plate under bead welding using inverse analysis was developed. Base on this inverse analysis, the inherent deformations are estimated by measuring the three-dimensional coordinates at a small number of selected points before and after welding. In this paper, the application of inverse analysis to typical welded joints, such as butt joint, lap joint, T-joint is discussed. By comparing the values of deformation components calculated by using the measured coordinates and those using inverse analysis, the effectiveness of the inverse analysis is confirmed. Then, reliability of the database for butt weld joint build by inverse analysis is also discussed in this paper.
Optimal design method is applied to hull design of Fast ships with SWATH type and Pod type hullforms. The main objective of this study is to find the optimal hullform for SWATH type ships with high speed operation. The SWATH type ships are well known with their outstanding motion performance in waves. On the other hand, their resistance has rather higher than conventional hullforms of monohulls and catamarans. However, reasonable hullform design using optimization method would reduce the resistance significantly, which would result that the SWATH type hullform to be suitable for the fast ship's hull. In this paper, a SQP (Sequential Quadratic Programming) method is adopted for the optimization. The generated optimal SWATH hullforms show that the cross sectional area of the hull is much reduced at the mid part of the hull, which results in lower wave resistance. On the contrary, the hull with straight cross sectional area shows higher wave resistance. The trade-offs between each hull are, then, discussed. Furthermore, the resistance of the pod type hulls is also examined.
The authors developed the computer system named optimum towing support system (OTSS) which can predict the drift motion, towline force, maneuvering method and needed horse power of the tow ship. The purpose of this research is to establish the techniques to prevent disabled ships from drifting and to tow them to the safety area in rough sea in order to prevent the secondary disaster such as collision, distress and explosion. There are 7 ship types including 2 kinds of tankers in the system. The hydrodynamic force acting on the disabled ships is calculated using 3 dimensional panel method in the OTSS system. The various ship status conditions such as capsize and breakage can be simulated. The hydrodynamic force of the tow and towed ship can be calculated in the computer system of OTSS. The motion and wave drift force of damaged and broken ships of various types in waves were calculated using OTSS in this report. The numerical calculation on the capsized condition was also done. The behavior of towed ships during towing was investigated. The numerical calculation was compared with the past experimental results concerning the broken tanker like 'Nakhodka'.
Reliability analysis has been performed to assess the ultimate hull girder strength in longitudinal bending. A series of progressive collapse analysis is performed applying the Smith's Method on hull girders of Panamax bulk carrier, Aframax tanker and wood-chip carrier to evaluate the ultimate hull girder strength and its sensitivities with respect to design parameters. On the basis of the calculated results, the mean and the standard deviation of the ultimate hull girder strength are derived applying the Mean-Value First Order Second Moment (MVFOSM) Method. On the other hand, time-dependent nonlinear ship motion is calculated to obtain wave-induced bending moment applying the Strip Method with consideration of the influence of large motion, and the mean and the standard deviation of the extreme wave-induced bending moment are derived. Utilising these results of calculations, probability of failure and reliability index are calculated and the ultimate hull girder strength in longitudinal bending is assessed.
Concern for the environment has increased in recent years throughout the world. With the development of the chemical production, NLS (noxious liquid substance) transportation has been increased in recent years, and the transportation of the chemical material poses a serious threat to the environment when it spills out, potentially to people far away from ship or terminal both in space and time. This paper deals with research on NLS danger in air. After research on environmental data (such as wind information, air temperature etc.), numerical analysis and PC calculation, the concentration and dose analysis of assumed accident in a port of Shanghai has been given out. Based on the concentration and dose data, some risk assessment of the accident has been given out, such as cancer risk and toxic risk. In the end, the authors try to give some suggestion to reduce the danger.
A marine environmental simulation is used to grope about the way of solving an environmental problem on the enclosed sea area. This technique including the ecosystem model, which details mainly the biological circulation of material, is evaluating the circulation quantity and the accumulation quantity, the ability of material to be purged away and so on quantitatively. The ecosystem model describes the material recycling of one piece of index material such as carbon, nitrogen, the phosphorus. Therefore, it is generally estimated that the other material circulates using the computed flux and the C-N-P ratio of the compartment. In this research, we point out that it isn't possible to do the correct evaluation using the conventional method, because the total amount of one piece of material is conserved but other materials are not saved. The C-N-P conservation model is proposed to keep total materials in ecosystem model.
In the previous paper, the authors introduced a method of seasonal adjustment into the Auto-Regression (AR) model prepared for the space-time analyses of seawater qualities measured in broad sea area. They showed that the AR-model with the seasonal adjustment would give estimates for a long term transition of seawater qualities. In the present paper, they discuss about characteristics of long-term trend, seasonal and auto-regressive component using several kinds of data obtained in Osaka bay for a long period of time. They show that the seasonal adjustment is effective, to keep the consistency of measured data at difficult time and position obtained by different organizations. They also show that the AR-components follow the laws of probability with a certain pdf. They finally conclude that the modified AR-model proposed as a suitable tool for the space-time assimilation of seawater quality data.
The authors have discussed space-time descriptions of seawater qualities in coastal sea area in Osaka bay in the previous papers introducing the Auto-Regressive mathematical model with seasonal adjustment considerations. They showed that the seasonal adjustment introduced in the mathematical model makes it possible to estimate the trend and seasonal components of seawater qualities from data observed for many years. They also showed that the AR-components of short-period recurrent phenomena fluctuate randomly like noise components. To solve the problem, they introduced a probabilistic approach to-the AR-components, and they showed that it is possible to treat the AR-components with the noise components as random variables In the present paper, they discuss more precisely about the understanding and treatment of AR-components that are not described properly due to the effect of time interval of observations, and about the possibility of the space-time assimilation of measured data introducing a 2-dimensional interpolation technique. They show that the AR-components have the same probabilistic characteristics as that of noise components in the analysis model, and that 2-dimensional interpolation is applicable to the space-time assimilation of measured data.
In this paper, a new technique for simultaneous measurement of the density and velocity fields is proposed. In the experiments, the regions with a density distribution are inserted between the camera and liquid crystal display, on which a picture of the random pattern are projected. The random pattern displacement was tracked before the density distribution changed. The gradient of the logarithmic function of the refractive index in the area was measured, and the density distributions are numerically reconstructed. Using PIV with above method, both density and velocity distributions of the gravity current were measured simultaneously, and they are in close agreement with conventional measurements.
The authors have been developing an evaluation method of facial expression in the previous reports. They demonstrated that facial expression can be quantitatively characterised by introducing the concept of the Fourier Descriptor (FD) and that the relationship between one's each individual facial factor such as an eye or a mouth and his/her psychological situation can be sufficiently expressed by the optimised discriminant analysis model. The present paper deals with overall evaluation of facial expression using the FDs of both eyes and mouth. The subjects were asked to exhibit the six fundamental emotions investigated in the field of psychology: happiness, surprise, fear, anger, disgust and sadness. The confidence level for each fundamental emotion was defined here as an individual evaluation of each facial factor. The multi-regression analysis was applied to relate facial expression to the six fundamental emotions and consequently contributions of each facial factor were obtained.
The final objects of this research are the construction of the weather routing system for a relatively small ship sailing in the coastal sea area and the assessment of this system for effects of safety and economic navigation. The weather routing is the optimum navigation based on weather and sea conditions which vary at real time. At first step of these objects, this paper deals with the estimation method of the ship position considering the ship maneuverability. The simulation results of a sailing ship in the tidal current were compared with the field's experimental results using an actual small ship. Comparing the simulated rhumb lines of a ship with the experimental ones, they showed reasonably good agreement. It was concluded that this simulation method for the ship positioning was effective for the weather routing system.
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