Research for Prevention of Capsizing of Small Ocean Sailing Yacht

2003年9月，一艘长6.45米的巡洋舰在日本琵琶湖进行抢风机动后倾覆沉没。事故的原因被认为是在抢风机动后突然加载的风所引起的横倾力矩超过了船舶的动稳定性。本研究以小型远洋帆船为研究对象，利用实船及缩比模型，以实验方式求得船体及风帆的阻尼系数及附加转动惯量，探讨其在突加风载下的动力稳定性及倾覆可能性。采用涡格法和基于NS/RaNS的CFD方法，通过数值计算获得了帆的定常性能，并分析了动态横摇运动对帆性能的影响。摘要提出了一种模拟方法来计算船体在风的突然作用下的横摇运动，并估算了船体在风的突然作用下的横摇运动直至倾覆的时间历程。模拟结果与模型试验结果吻合较好。计算出的倾覆临界风速与事故发生时的风况相吻合。根据这些数据，研究了相对较小的帆船的主尺度，并建立了三种典型的船型。采用数值模拟的方法对这些船舶的倾覆临界风速进行了估算。通过分析，阐明了船员体重对船体的影响，并建立了倾覆临界风速-位移关系图。本海图将用于防止小型远洋帆船倾覆。

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.