Full-Scale Research on the Hull Form Improvement by Bulge

与其他船只相比，渔船容易倾覆。指出渔船作业强度大、装载条件管理不善以及船舶主体尺寸的限制是造成渔船稳定性较差的原因。根据最近发生的“龙湖丸V号”拖网渔船倾覆事故，日本国土交通省强制检查现有渔船的稳定性，如果稳定性不够，就要提高稳定性。为了提高船的稳定性，在船的侧壁加装鼓包是最好的解决方案之一。然而，凸起通常使船体阻力和速度损失显著增加。本文通过对原渔业科考船“Ushio-maru”号的模型试验和放大后的原渔业科考船“Ushio-maru”号的全尺寸试验，探讨了凸起对船舶稳定性的影响。主要结果总结如下：(1)从船体周围流场的角度阐明了凸起对船体阻力的机理，提出了采用朗肯源法设计凸起形式的合适方法。该方法已应用于“Ushio-maru”的实际伸长设计中，并通过模型试验和全尺寸试验得到了验证。(2)在理论和试验的基础上，研究了凸包式船体的操纵和耐海性能。结果表明，设计良好的凸起对这些性能没有影响。

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.