Research for Prevention of Capsizing of Small Ocean Sailing Yacht

2003年9月，在日本琵琶湖，一艘长6.45米的全帆巡洋舰在进行航向机动后倾覆沉没。该事故的原因被认为是由于在船尾操纵后由于风的突然载荷引起的倾侧力矩超过了船的动稳定性。本文研究了小型远洋帆船的动力稳定性和在风的突然载荷作用下倾覆的可能性。利用全尺寸船艇和比例模型实验得到了船体和船帆的阻尼系数和附加惯性矩。在此基础上，采用数值计算方法，利用涡格法和基于NS/RaNS的CFD方法，获得了风帆的稳态性能，并评估了动态滚动运动对风帆性能的影响。一个数值。提出了一种计算船在风的突然载荷作用下的横摇运动的仿真方法，并估计了船的横摇运动直至倾覆的时程。模拟结果与倾覆模型试验吻合较好。估计的翻船阈值风速也与事故发生时的风况相吻合。研究了相对较小的巡洋舰的主要尺寸，并根据这些数据创建了三种典型的船型。采用数值模拟的方法对这些船进行了倾覆的阈值风速估算。在此基础上，明确了船员重量对船的影响，并建立了倾覆时的位移-阈值风速图。本海图将用于防止小型远洋帆船的倾覆。

In September 2003, a 6.45m length over all sailing cruiser capsized and sunk just after tacking maneuver operation at the Lake Biwa in Japan. The reason of this accident is considered that the heeling moment due to sudden loading of the wind just after tacking maneuver exceeded dynamic stability of the boat. In this research, dynamic stability and possibility of capsizing by sudden loading of the wind are investigated for small ocean sailing yachts.Damping coefficients and added moments of inertia of the hull and sail were obtained experimentally using a full-scale boat and a scaled model. Then numerical calculation methods were employed to obtain the steady sail performance and to evaluate the effect of dynamic rolling motion on the sail performance using vortex lattice method and NS/RaNS based CFD method.A numerical. simulation method was proposed to calculate the rolling motion of the boat due to sudden loading of the wind, and time histories of rolling motion up to capsizing of the boat were estimated. The simulated results agreed well with the capsizing model test. The estimated threshold wind velocity for capsizing was also coincided with the wind condition at the accident.The principal dimensions of relative small sailing cruisers were investigated and three typical boat configurations were created from these data. The numerical simulation method was adopted for these boats to estimate the threshold wind velocity for capsizing. From this analysis, the effect of crew weight on the boat was clarified, and a chart for Displacement to threshold wind velocity for capsizing was established. This chart will be used for prevention of capsizing of small ocean sailing yachts.