In this study, the applicability of CFD to the design of the optimal arrangement of hull FIN, which is one of the energy-saving devices, was investigated. Considering the calculation environment at the design site of a shipyard, CFD with overset grid approach was applied because it is possible to maintain the accuracy for estimating the energy-saving effect with a small number of grids. The hull FIN is attached to the JBC hull form, and the effect of the installation position in the front/rear and vertical directions on the energy-saving effect was investigated. As a result, it was found that the main reason for the performance improvement by the hull FIN was the wake gain by moving the position of the stern vortex to the outer circumference of the propeller circle. From this, it was also shown that this method is effective for understanding the performance improvement mechanism of energy-saving devices.

　Recent years, merchant ships are equipped not only with high performance propeller, but also with multiple ESDs (Energy Saving Devices) to recover energy losses, so propulsion performance has been greatly improved. There is a possibility that propulsion performance can be improved by integrating propeller and multiple ESDs.

　In our previous study, the self-propulsion test results with the multiple ESDs like stern duct and rudder bulb showed the highest energy-saving effect, namely 15.0% compared with bare hull. In addition, the maximum difference of BHP (Brake Horse Power) caused by differences in propeller position and pitch distribution was 4.9%. The PIV (Particle Image Velocimetry) measurement results confirmed that the flow field in front and behind the propeller changed depending on the propeller position and pitch distribution, and the interaction among the propeller and the ESDs also changed.

　After the previous study, additional self-propulsion tests including rudder resistance measurements were conducted using propellers having three different pitch distributions and the multiple ESDs. Furthermore, the flow field changes in front of the rudder due to the presence of stern duct and the difference of propeller pitch distributions were analyzed by PIV measurement results. In this paper, the authors focus on the thrust deduction factor and describe the energy-saving effect due to changes in rudder resistance.

　A new risk assessment method for anchor dragging is proposed. Using several kinds of information that can be commonly obtained on the navigational bridge of ships, the touch down point of the anchor chain to the seabed is estimated based on the ship’s equations of motion. Firstly, accelerations and velocities of the ship are numerically evaluated using GPS data. Secondly, the hydrodynamic forces, such as added mass, damping force and wind force, are estimated based on the theory of ship maneuverability. Thirdly, the tension of the anchor chain is determined as a residual term of the equations of motion. Finally, the touch down point of the anchor chain to the seabed is estimated based on the catenary theory. In this study, the point is named as the Virtual Touch Down Point (VTDP) and used for estimation of the length of the anchor chain crawling on the seabed and its holding power.

　The new method was applied to the data set measured on an actual single anchored ship and the relationship between the chain length crawling on the seabed and the wind was investigated in the form of time series. The results show a negative correlation between them, suggesting the usefulness of VTDP. Therefore, it was confirmed that the method proposed in this study is effective for risk assessment of anchor dragging.

　In this study, a wear amount estimation method is investigated using the data obtained from the 2^nd Demonstration Experiment of the wind observation system off the coast of Sakata, the floating platform including the mooring system to reduce wear is optimized by using the estimation method. First, the wear condition of the mooring lines is investigated and it is found that the wear amount at the mooring point on the buoy side is the largest. Next, the cause of the higher progress wear than the expected design speed is investigated by numerical calculations, and it is confirmed that the proportionality constant in the wear evaluation formula proposed by Takeuchi et al. is changed according to the sea conditions, and the proportionality constant in the equation is determined. Finally, the floating platform including the mooring system is optimized by using the proposed method to reduce the wear amount of the mooring line, it is found the wear amount can be reduced by adjusting the length of the mooring line or the reduction of buoy weight

　With a vertical circular cylinder with infinite draft taken as a simplified model of spar-buoy type offshore wind turbine, a review of theoretical analyses for the linear diffraction problem and the second-order wave drift force is provided. For the linear solution of the velocity potential, it is confirmed that Bessho’s analytical solution method for an integral equation in the source distribution method provides the same result as that by the eigenfunction expansion method. For the wave drift force, the near-field and far-field methods are reviewed, showing that the same explicit-form analytical solution can be obtained. Then, it is also shown that Bessho’s method applying Lagally’s theorem gives the same analytical result for the wave drift force, and furthermore, Tsubogo’s calculation formula given in a reciprocal form on the body surface can be regarded as the same in form as that by the Lagally’s theorem. As a consequence, it is proven that exactly the same analytical result for the wave drift force can be obtained even from Tsubogo’s expression.

　This paper presents a method for estimating the sectional loads along ship hull girder in real-time by combining a Kalman filtering algorithm and a mode superposition method, as part of digital twining system. The developed method is applied to a full-scale measurement on an 8600 TEU container ship and the strain signal at several locations is used as inputs to estimate hull deformation and external loads. The stress distribution at deck level due to vertical bending moment, and horizontal and torsional moment distributions are presented and discussed. Then, the method is extended for identifying whipping and springing events. It is justified by comparing with other methods that have been accepted so far. The effects of whipping and springing on fatigue damage are respectively analyzed by separating the wave-induced vibrations into whipping and springing. It is shown that the fatigue damage caused by the wave-induced vibrations is significant and the fatigue damage caused by springing is equivalent to, or even larger than the one by whipping.

　This research aims to assess the optimum route proposal system for a four-hull automated navigation vessel ”Quad-maran” by conducting actual sea tests and simulations. The route proposal system is mainly built based on considerations of obstacle avoidance, navigation performance, and operation of multiple vessels. In this paper, the optimal route proposed in the simulations will be verified with the actual sea tests focusing on two aspects. Firstly, it is verified that the proposed patrol route is appropriately executed from the actual sea test results. Secondly, the simulation to incorporate and operate multiple vessels is developed. From the results, it has been found that the cruising time predicted in the simulation is different from the actual cruising time in actual sea tests. An attempt is made to understand the error in cruising time for each section of the patrol route. A simulation of using two vessels is also shown as a demonstration. Further, the disadvantages of clustering measurement points in the K-means method are also clarified.

　In this paper, the authors propose the offshore installation time estimation model for floating offshore wind turbines, hereinafter FOWTs, in order to analyze the efficiency in each offshore installation process. The total offshore installation time as the sum of operational time for (1) pre-anchoring, (2) ultimate holding capacity verification, (3) towing, (4) mooring, and (5) the other operational processes is defined. This study introduces “installation time per mooring line” as benchmark to measure of efficiency. Firstly, the authors applied this proposed model to Japanese and European FOWTs project data, and it is found that in Japan, the installation time per mooring line for (2) ultimate holding capacity verification and (4) mooring was reduced by 69% and 95%, respectively from the initial time. Secondly, the authors also applied this model to the offshore installation of a large-scale wind farm, by changing the benchmarks when the number of mooring lines of FOWT and the distance from the port were varied under the constraints of the port occupancy duration. To satisfy the duration of pre-anchoring port occupancy, it is concluded that the summation of installation time per mooring line for (1) pre-anchoring and (2) ultimate holding capacity verification should be reduced to the same level as that of Europe, and by almost 84% from the present level.

　This paper presents an assessment of the performance of a Crew Transfer Vessel (CTV) in transfer mode to a floating substation using P-plot chart and discusses on the influence of the motion characteristics of the CTV and her horizontal fender force. The results suggested that there is almost no shielding effect of the structure at the slip limit and the effect of floating substation's motion is small on the CTV motion. In addition, the difference of slip characteristic due to the berthing direction is small, and the slip limit value is higher in the floating type than in the fixed substation. Three different joint's torsional stiffness around the z-axis has been tried and it is found that the influence on the P-plot based only on the vertical joint force is small, which implies that the symmetrical and antisymmetrical motions are not coupled even when she is berthing. On the other hand, the effect of torsional stiffness is clearly appeared in the antisymmetric motion spectrum and the joint horizontal force. As a result, the torsional stiffness has generally a considerable effect on the slip limit considering both the vertical and the horizontal joint forces except for a small torsional stiffness. The wave surface elevation and the rotation of the floating substation due to the berthing of the CTV are also discussed as other factors.

　The damage caused by the Nankai Trough earthquake is expected to be extremely extensive and severe. From the term of about eight days after the disaster (called “pull-type” transportation period) until reconstruction period there will be a huge transportation demand of goods that far exceeds the capacity of trucks. If transportation cannot be carried out sufficiently, there will be social disorder in the early stages due to shortages of food and beverages, etc. and later, delay of recovery and reconstruction lead to various other problems, like lost economic opportunities, perpetuation of poverty, rising costs of reconstruction, and so on. To mitigate them, ships can be expected to play a large role since they can transport a large amount of goods over long distances with a small number of people. This paper supposes the largest type of Nankai Trough earthquake and evaluates the available quantities of ferries, RORO ships and general cargo ships using static and dynamic methods. In the analysis, since the dynamic evaluation result depends greatly on ships’ position and their navigational status at the date and time of the disaster, the evaluation is performed using long-term ship specification data base and AIS (Automatic Identification System) data for whole Japan. It is possible to obtain the current available transport capacity of ships and its future prospects after the disaster.

In this paper, an evaluation method for effects of zero emission fuels on ship designs is proposed, and its usefulness is demonstrated by trial examples as follows, 1) A method to combine the price of alternative fuel and the additional cost on bunkering facility with the design development of individual ship under variable conditions is proposed. 2) From a trial analysis for an Aframax tanker, conditions in which an alternative fuel becomes superior from a cost aspect are shown in connection particular ship designs. 3) Possibility of a total simulation which gives the optimum design for particular ships under conditions of fuel supply and ship operation, are shown using the proposed method.

Shipbuilding is one of the most complex production systems in the manufacturing industry because of the incredible variety of parts and highly complex processes. However, production plans are currently prepared manually depending on the experience of expert workers. In this paper, a production planning method based on shipbuilding process simulation is proposed for use in actual shipyards, which simultaneously satisfies the needs of both production managers, who require on-time delivery plans, and field workers, who aim to minimize waiting time and improve operating rates. Specifically, the authors developed a hybrid method that combines backward and forward simulation for planning front-loading to meet deadlines and reduce waiting time. In the case study, the method was applied to a sub assembly conveyor line in an actual shipyard to demonstrate the validity and feasibility of the simulation results.