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

本研究的目的是利用船体的俯仰或翻滚等振动引起的柔性帆的畸变来研究增加风帆推力的机理。首先，通过数值计算估计了纵摇和横摇运动对船帆力的影响。数值计算方法采用涡点阵法，每次均有脱落涡丝向下游移动。计算结果表明，俯仰运动，特别是横摇运动可以提高船帆的推力。另一方面，在一艘全尺寸帆船上，用帆力测力仪测量了各种船只运动下的帆力。帆力测力仪由一个铝制框架组成，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。在此基础上，构造了一种船帆畸变系统，使其在船身振动作用下产生几乎相同的畸变形状。该系统由两个电动执行器组成，安装在测功机机架的平台上。执行器将风帆控制片或桅杆弯曲控制索送入或送出，并以特定的扭转角度不断地扭曲风帆形状。该系统表明，连续畸变引起的风帆力变化范围大于静态变化情况。由此可以认为，建立了船舶振荡引起的船帆推力增大机理的研究体系。对风帆连续畸变的数值计算仍在继续，并将计算结果与实测结果进行了比较。从这些结果中，柔性风帆提高推力性能所需的特性将变得更加清晰。

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.