Study on Estimation of Deck-Wetness for a High-Speed Vessel

我们已进行了三年(1996-1998)的研究项目，题为“高速船甲板湿度估算研究”。主要结论如下：(1)船舶定常绕流对船舶上的非定常水动力有很大影响。我们开发了一种新的方法来预测它们之间的相互作用。研究表明，定常流势的二阶导数项对水动力起着重要的作用。(2)发展了一种实用的计算定常与非定常相互作用影响的线性朗肯面元法。此外，与试验结果的对比表明，该方法对于高速船舶耐波性的预报是有效的。(3)定常流动对辐射力的影响较大，而对绕射力的影响较小。特别是，在低频…中，它强烈地出现在他们身上(4)为了准确估计船舶的压力分布，不仅要考虑自由表面条件的影响，还要考虑船体表面条件的影响。(5)可以通过在船头的转角来减小船首部分绕射波的幅度。因此，希望在船头部分安装转向节，以减少甲板在高处的湿润度。恒定流和非恒定流之间的影响随着前进速度的增大而变得更加显著。其中，船首部分附近的波浪型受船首耀斑形状的影响较大。因此，为了准确地预测高速船的耐波性，有必要发展一种新的预报方法来考虑静水面以上的船头耀斑的影响。(7)研究表明，大多数高速船的事故都与高速船舶的不稳定运动密切相关。因此，迫切需要弄清产生不稳定运动的水动力现象。较少

We have performed the Research Project titled "Study on Estimation of Deck-Wetness for a High-Speed Vessel" for three years (1996 - 1998). The main conclusions obtained in this study are summarized as follows :(1)It was made clear that steady flow around a ship strongly affects unsteady hydrodynamic forces on a ship. We developed the new method predicting the interaction effect between them. It was made clear from this study that the second derivative term of steady flow potential plays important role on hydrodynamic forces.(2)We developed 3.D linear rankine panel method to predict the interaction effect between the steady and unsteady flow as a practical estimation method. Furthermore, it was made clear from the comparison with experimental results that this method was useful for predicting the seakeeping qualities of a high-speed vessel.(3)The steady flow strongly affects on radiation forces rather than diffraction forces. In particular, it strongly appears on them in the low frequen … More cy range.(4)The influence of steady flow has to be taken into account not only the free surface condition but also the ship hull surface condition to estimate accurately the pressure distribution on a ship.(5)The amplitudes of diffraction waves at bow part can be reduced by the knuckle at bow part. Thereby it is desirable to attach the knuckle at bow part to decrease the deck wetness on a high. speed vessel.(6)The influence between steady flow and unsteady flow becomes more remarkable as the forward speed increases. In particular, wave profile around bow part is strongly affected by the bow flare form. Thereby, It is necessary to develop a new predicting method which can take into account the effect of bow flare form above the still water surface in order to predict accurately seakeeping qualities of a high-speed vessel.(7)It was made clear that most of accidents for high-speed vessels are strongly related to unstable motions of high-speed vessels. Thereby, it is urgent to make clear hydrodynamic phenomena generating the unstable motions. Less