Method for Mathematical Description of Ship Form and its Application

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The research project was carried out (1)to describe, e.g. parameterize, ship "form" quantitatively using the "Fourier Descriptors", and (2) to apply the results as a tool for obtaining/estimating the relation between ship performance and ship form that experienced designers have learned and understood empirically and metaphysically throughout their long-period design worksAs the first step, surveys of researches which can be used for parameterizing 'formt' were carried out, and the "Fourier Descriptors" was found out an appropriate method for describing/expressing "form". Only 6 terms of Fourier Descriptors are found sufficien to describe practically complicated and delicate ship frame lines.The method developed in the study was applied for estimating hydrodynamic forces, wave damping coefficient and added mass coefficient, acting on ship body oscillating in waves. Results of estimation by the method was proved to give good estimates compared with the results obtained by using the well-known "Lewis Form Transform" and the "Ursell-Tasai Method". It was made clear that the present method has an advantage for describing/evaluating delicate change of frame lines and resulting hydrodynamic forces.Another very important application of the present method was understanding/evaluating relations between configuration of ship's aft-body, frame lines of aft-body, and self-propulsion factors obtained from model experiments in a towing tank. It was made clear that the present approach can explain the efforts done by experienced ship designer/engineer for improving propulsive performance of ships in the initial ship design are reasonable, and the Fourier Descriptors would be a efficient tool to describe/improve/evaluate the complicated and delicate ship form that has been retrieved experienced ship engineers exclusively.