Method for Mathematical Description of Ship Form and its Application

本研究的目的是：(1)利用“傅立叶描述符”对舰船“形”进行定量的参数化描述；(2)将研究结果作为一种工具，用于获取/估计有经验的设计者在其长期的设计工作中通过经验和形而上学所了解的船舶性能与船型之间的关系。作为第一步，对可用于“形”参数化的研究进行了综述，找到了一种描述/表达“形”的合适方法。仅用6项傅里叶描述子描述了实际复杂而精细的船体骨架线型，并将该方法应用于船体在波浪中振动时的水动力、波阻尼系数和附加质量系数的估算。与著名的“Lewis形式变换”和“Ursell-Tasai方法”的估计结果相比，该方法的估计结果具有较好的估计效果。该方法的另一个重要应用是了解和评价船体尾部外形、尾部骨架线型与拖曳水池模型试验所获得的自航系数之间的关系。结果表明，该方法可以解释有经验的船舶设计者/工程师在船舶初始设计中为改善船舶推进性能所做的努力是合理的，傅立叶描述子将是描述/改进/评估已由有经验的船舶工程师独家检索到的复杂而精细的船型的有效工具。

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.