Study on Unstable Phenomena in Transverse Stability for High Speed Craft

众所周知，高速船的横向稳定性即使在静止状态下具有足够的静稳定性，在超过一定航速时也会出现不稳定现象。这种现象比较复杂，很难对其产生的机理进行深入的研究。本文旨在阐明高速船横向稳定性失稳现象的机理。利用Maruo的细长船体理论，对一艘3.6m船长的船模进行了船体动压的数值计算，结果表明，船体的横倾力矩随航速的增加而增大，特别是在Over Froud数为0.8时，船体的横倾力矩随航速的增大而增大。通过船模试验验证了这一趋势。从这些研究中可以看出，作用在船体上的动压随航速的增加而发生变化，是横向稳性不稳定现象的主要原因之一。同时，动压力沿纵向的分布会发生变化，从而产生横摆力矩。

It is well known that the transverse stability of a high speed craft might occur the unstable phenomena at running more than a certain speed even though the stability possess adequate static stability at rest condition. The phenomena of this kind are complex, and it will be difficult to investigate the mechanism of the phenomena.This paper is to clear the mechanism of unstable phenomena of transverse stability in high speed craft. The numerical calculations for the dynamic pressure acting on ship's body were carried out on a model craft with ship's length 3.6m by using slender body theory of Maruo.According to the results of numerical calculation, the heeling moment of the craft increased with ship speed increasing, specially with over Froud's number 0.8. This tendency on phenomena was verified by the model test.From these investigations, one of the main reason for unstable phenomena in transverse stability is that the dynamic pressure acting on ship's body changes with ship speed increasing. Simultaneously the distribution of the dynamic pressure will change along to the longitudinal direction, then this pressure causes yaw moment.