Development of Flexible Sail to Improve Thrust Performance by Using Oscillation of Sailing Vessel

本研究旨在探讨利用帆船摇摆等振动引起的挠性风帆变形来增加风帆推力的机理。首先，通过数值计算来估计纵摇或横摇运动对风帆作用力的影响。数值计算采用涡格法，涡丝的脱落在每个时刻都在下游进行。计算结果表明，纵摇运动特别是横摇运动提高了风帆的推力。另一方面，在一艘全尺寸帆船上利用帆力测力仪测量了不同船型运动下的帆力，该测力仪由一个铝制框架通过几个称重传感器固定在船体上。将计算结果与实测值进行了比较，验证了计算方法的准确性。然后，构建了风帆变形系统，生成了与实测值基本相同的船体摆动变形形状。该系统由安装在测功机机架平台上的两个电动执行器组成。执行机构将风帆控制片或桅杆弯曲控制线送入和送出，并在特定的扭角下连续变形风帆形状。结果表明，连续变形引起的风向力变化幅度大于静力变化情况，由此可以认为，建立了船体摆动引起的风帆推力增大机理的研究体系。对风帆连续变形的数值计算仍在继续，并将计算结果与实测值进行了比较，从中可以明确柔性风帆提高推力性能所需的特性。

This research aims to investigate an increasing mechanism of sail thrust using distortion of the flexible sail caused by oscillation of a sailing vessel such as pitching or rolling. First, numerical calculations were performed to estimate the variation of sail forces by pitching or rolling motion. The vortex lattice method was adopted as the numerical calculation method, where shedding vortex filaments proceeded downstream in each time. The calculated results showed that the pitching motion and in particular rolling motion improved thrust of sail. On the other hand, sail forces under various kinds of boat motion were measured in a full-scale sailing boat with the use of a sail force dynamometer, which consisted of an aluminum frame fixed to the hull by way of several load cells. The calculated results were compared with the measured and the accuracy of calculation method was confirmed.Then, a sail distortion system was constructed to generate almost same distorted shape due to the boat oscillation. This system consisted of two electric actuators, which were set on the platform of the dynamometer frame. The actuators fed in and out the sail control sheets or mast-bend control wires, and distorted the sail shape continuously in particular twist angle. This system showed that the variation range of sail force caused by the continuous distortion was larger than the case of static change.From this research, it can be considered that the investigate system of an increasing mechanism of sail thrust due to the boat oscillation has been established. The numerical calculations for the continuous distortion of the sail are still continuing, and the calculated results have been compared with the measured.From these results, the required characteristics for the flexible sail to improve thrust performance will become clear in detail.