Prediction of Effects of Hull Forms on Seakeeping Qualities of Ships

本研究的目的是发展一个系统的方法来预测在波浪中的附加阻力和船舶的安全性下的甲板浸湿的影响。这种系统的方法将有助于从耐波性评价船体形状。现有的几种方法不一定能达到这一目的。它们不能给出准确的预报，不能正确地反映船体形状之间的微小差异的影响。因此，我们需要开发新的方法，特别是在甲板上的水的影响下的附加阻力和瞬态运动导致倾覆，因为这些还没有得到充分的研究到目前为止。本文给出了几组实验数据，以清楚地表明船首形状对船舶在波浪中航行时产生的非定常波型的影响。本文提出了一种新的理论方法来描述这一效应，从而大大提高了对弓形变钝时附加阻力的预测精度。2.研究了一种考虑有限幅运动效应的水动力计算方法。3.我们成功地提供了当海水越过舷墙到达甲板时船舶倾覆的计算机模拟。该模拟程序使我们能够评估舷墙高度对船舶安全的影响。4.采用三维面元法，精确满足船体表面的边界条件，即使在斜浪和随浪中也能预测附加阻力。该方法在计算技术上作了一些改进，可用于从附加阻力的角度评价差别不大的船体外形。

Objective of this study is to develop a systematic method for predicting added resistance in waves and safety of a ship under the effects of deck wetting. Such systematic method will be useful for evaluating hull form from its seakeeping qualities. Several methods available do not necessarily serve this purpose. They do not give accurate prediction which reflect correctly the effects of a little difference between hull forms. So we need to develop new methods particularly for added resistance and transient motions leading to capsize under the influence of water on deck, since those have not been fully investigated so far.What we have done in this study are as follows: 1. We presented several experimental data to show clearly bow shape's effect on the unsteady wave pattern generated by a ship running in waves. This effect was described by a new thoretical approach we developed, accuracy of prediction of added resistance when bow shape is blunt is improved considerably by this new method. 2. A simple method was investigated for computing hydrodynamic forces with the finite magnitude effects of motion taken into consideration. 3. We succeeded in providing computer simulation of capsizing when sea water is coming onto deck over bulwark. This simulation program enables us to evaluate the height of bulwark on the safety of ships. 4. 3D panel method in which the boundary condition on the hull surface is accurately satisfied was applied for predicting added resistance even in oblique and following waves. With some improvements in computational technique, this method is useful for eavaluating hull forms with a little difference from the standpoint of added resistance.