Method for Mathematical Description of Ship Form and its Application

该研究项目的目的是（1）使用“傅立叶描述符”定量地描述船舶“形状”，例如参数化，（2）将结果用作获得/估计船舶性能与船舶形状之间关系的工具，这些关系是经验丰富的设计师在其长期设计工作中经验地和元认知地学习和理解的。摘要对可用于“形式”参数化的研究进行了综述，发现“傅立叶描述子”是描述/表达“形式”的合适方法。用该方法计算了船体在波浪中振动时所受的水动力、波浪阻尼系数和附加质量系数。与著名的“刘易斯形式变换”和“Ursell-Tasai方法”的估计结果进行了比较，证明了该方法的估计结果是好的。结果表明，该方法在描述和评价船体骨架线的细微变化及由此产生的水动力方面具有优越性，其另一个重要应用是理解和评价船舶尾体外形、尾体骨架线与拖曳水池模型试验所得自航因子之间的关系。结果表明，该方法可以解释经验丰富的船舶设计师/工程师在船舶初始设计阶段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/评估复杂精细船型的有效工具，这是经验丰富的船舶工程师所独有的。

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.