Full-Scale Research on the Hull Form Improvement by Bulge

与其他船只相比，渔船倾覆的情况更严重。可以指出，渔船稳性差是恶劣作业和装载管理不善以及船舶主尺度限制的基础。日本国土交通省根据最近发生的"Ryuho-maru V"号拖网渔船倾覆事故，对现有渔船的稳性进行了检查，如果稳性不够，就必须对其进行改进。对于稳定性的改善，在容器的侧壁上安装凸起是最好的解决方案之一。然而，凸起通常会显著增加船体阻力并损失速度。本研究以渔业研究船"Ushio-maru"的原型船和扩建船为基础，通过模型试验和实船试验，探讨了鼓包对船舶性能的影响，不仅是对稳性的影响。主要结果如下。(1)从船体流场的角度阐明了鼓包对船体阻力的作用机理，并利用朗肯源法提出了合理的鼓包形状设计方法。该技术已应用于“Ushio-maru”的实际伸长设计，并已通过实验模型试验以及全尺寸试验得到证实。(2)本文还从理论和试验两方面研究了鼓形贴体船体的操纵性和耐波性。结果表明，设计合理的凸台不会对这些性能产生影响。

Fishing boats suffer from much capsizing as compared with other vessels. It may be pointed out that the stability of fishing boats tend to be poor as the bases of the severe operations and the poor management of loading condition as well as the problem with the restrictions of principal dimensions of ship. According to the recent capsizing of the trawler "Ryuho-maru V", Ministry of Land, Infrastructure and Transport of Japan forced to check the stability of existing fishing boats and to improve the stability if not enongh. As for the improvement of the stability, the fitting of a bulge on sidewall of the vessel is one of the best solutions. However, the bulge generally makes a significant increase of hull resistance and loss of speed. In this research, we have investigated into the effect of the bulge on the ship's performances not only on the stability, based on the model experiments and the full-scale experiments of original and enlarged fisheries research ship "Ushio-maru". The principal results are summarized as the followings.(1) The mechanism of the hull resistance by a bulge has been clarified based on the view point of flow field around hull, and the suitable method to design the bulge form has been proposed using Rankine's source method. This technique has been applied to the actual elongation design of "Ushio-maru", and it has been confirmed by the experimental model tests as well as the full-scale trials.(2) The manoeuvring and sea-keeping performance of the bulge-fitted hull form has been also investigated based on theoretical and experimental tests. As the results, the well-designed bulge does not affect on these performances.