Noritaka Hirata

A Study on the Optimization of Ship Design Process Using Wildcard GA

The performance of the product and the design time are influenced by the design process. Therefore, it is very important to advance the design in an appropriate design process. However, the design process generally relies on the experiences of the designer and it is difficult to examine their characteristics. In this study, design process of ship principal particulars is optimized by using the optimization technique. Moreover, the features of the optimized design processes are examined. Characteristics of this paper are following points; (1) The optimum design process is generated by using the Wildcard Genetic Algorithm which can deal with the uncertainty of product information. (2) By executing the optimization, two kinds of design processes are generated i.e. performance valuing process and feasibility valuing process. (3) Characteristics of the optimized design processes are analyzed by using the design support system in which dependency of the information and changes in the variation range of constraints and objective functions according to the progress of the design are visualized. In this paper, optimization method of design process and the results of the optimization are shown. Moreover, overview of the design support system and features of the optimized design process are discussed. As a result, effectiveness of the proposed system is confirmed.

Launching Simulation of a Ship

This paper presents a practical simulation model for ship launching taking the dynamic coupling effect of trim angle change and vertical motion into account. The motion equations were derived in three stages of sliding, lift by stern and afloat modes in launching. By solving the motion equations in three stages continuously, ship speed change, trim angle change, traveling distance, pivoting load, etc. during launching can be calculated. To obtain the validation data of the simulation method, a fullscale test was carried out to measure the ship motions during launching by a Kinematic Global Positioning System (KGPS) system. Then, three antennas for KGPS were arranged on a Chip Carrier with 191.5 m in ship length. Some parameters needed for the simulation were determined by comparing with the fullscale test result. The present simulation method is useful for capturing th ship launching behavior.

Time Domain Simulation of Wave-induced Motions of Tow and Towed Ships in Head Seas

A time domain simulation method for wave-induced motions of tow and towed ships in head seas is presented. The present method uses a 2D lumped mass method for expressing the dynamics of towline, and so can take into consideration the effects of self-weight and deformation of towline and the fluid resistance acting on it. The present method can calculate not only wave-induced motions of tow and towed ships but also tension acting on a towing point in time domain. In order to validate the present method, using a ship model with twin podded propellers as tow ship and SR108 container ship model as towed ship, the simulations of wave-induced motions of tow and towed ships and tension acting on a towing point were made in various wave lengths and the calculated results were compared with the model test results. As a result, although there is some room for improvement, the present method can roughly capture the wave-induced motions of tow and towed ships and tension behavior during towing in head seas.

Application of KGPS for Ship Trial

Abstract Kinematic GPS(KGPS) can measure a position with high accuracy. By using of more than three GPS antennas, six Degree Of Freedom motion at any points can be calculated. From experiment data, it is shown that the position at center of gravity can be measured excluding rolling motion. Next the effects of KGPS accuracy and ship distortion to rolling motion measurement. Lastly the example of calculation of hydrodynamic coefficients is shown.