Full-Scale Research on the Hull Form Improvement by Bulge

与其他船只相比，渔船倾覆的风险更大。可以指出，渔船稳性往往较差，这是作业严酷、装载条件管理不善的基础，也是船舶主尺度限制的问题。根据最近发生的“Ryuho-Maru V”号拖网渔船倾覆事件，日本国土交通省被迫检查现有渔船的稳定性，并提高稳定性，如果不够的话。对于稳定性的提高，在船体侧壁安装凸起是最好的解决方案之一。然而，鼓包一般会使船体阻力和速度损失显著增加。在本研究中，我们在船模试验和扩大的“Ushio-Maru”号渔业科考船的实船试验的基础上，研究了鼓包对船舶性能的影响，不仅对稳性有影响。主要研究结果如下：(1)从船体周围流场的角度阐明了鼓包阻力的机理，提出了采用朗肯源法设计鼓包形式的方法。该技术已应用于“Ushio-Maru”的实际加长设计中，并得到了船模试验和实船试验的验证。(2)在理论和试验研究的基础上，对鼓形船型的操纵和耐波性进行了研究。结果表明，设计合理的鼓包不会影响这些性能。

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.