Research for Prevention of Capsizing of Small Ocean Sailing Yacht

2003年9月，一艘全长6.45米的巡洋舰在日本琵琶湖进行追尾机动作业后倾覆沉没。事故发生的原因被认为是侧倾操纵后由于风的突然作用而产生的横倾力矩超过了船的动力稳定性。本文研究了小型远洋帆船的动力稳定性和风致倾覆的可能性，通过实船和缩尺模型试验得到了船体和风帆的阻尼系数和附加转动惯量。然后利用涡格法和基于NS/RANS的CFD方法，通过数值计算的方法得到了定常风帆的性能，并评价了动态横摇运动对风帆性能的影响。提出了一种模拟船体在突发性风荷载作用下横摇运动的方法，并估算了船体倾覆前横摇运动的时程。模拟结果与倾覆模型试验结果吻合较好。估计的倾覆阈值风速也与事故发生时的风况相吻合。对相对较小的帆船的主要尺寸进行了调查，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，估算了发生倾覆的门槛风速。在此基础上，明确了船员重量对船舶倾覆的影响，并建立了倾覆临界风速与排水量的关系图。这张图将用于防止远洋小型游艇倾覆。

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.