操縦性流体力の過渡特性に関する研究

国际海事组织（IMO）的船舶操纵性临时标准迫切需要在设计阶段对船舶操纵性进行预测。在这个预测研究项目中，我们测量了作用在船体上的水动力的过渡特性，并试图通过过渡特性来估计稳态下的水动力。首先，研究了船舶模型附加质量的估算方法，这是分析船舶运动中水动力作用的必要条件。在此基础上，通过模型试验，提出了一种简单的附加质量测量方法，并绘制了块状船舶附加质量估算简图。我们还开发了一种不需要进行模型实验的CFD估算增加质量的方法。其次，我们研究了机动运动中水动力的分量型数学模型，以理解力的作用机理。在本研究项目中，我们对几种船模进行了斜拖试验，以了解水动力的过渡特性。用分力型数学模型对水动力时程进行了分析，得出以下结论：横流阻力分量是影响过渡效应的重要因素。在匀速运动开始时，横截面为矩形的船舶的横流阻力很快达到稳态。另一方面，实际船舶的横流阻力需要较长时间才能达到稳态。粘性升力分量的过渡作用在船首比在船尾更为突出。但对总水动力的影响很小。从上述结果来看，似乎可以从斜拖曳运动的过渡特性中大致估计稳态时的水动力。

The interim standards of ship maneuverability by IMO are badly in need of the prediction of ship maneuverability at design stage. In this research project for the prediction, we measured the transitional characteristics of hydrodynamic forces acting on ship hulls and tried to estimate the hydrodynamic forces in steady state from the transitional characteristics. First, we studied a method to estimate the added mass of a model ship, which is indispensable to analyze hydrodynamic force acting on the ship in motion. From this study, we developed a simple method to measure the added mass by a model experiment and made out a quick chart of the added mass estimation for block type ship. We also developed a method to estimate the added mass by using CFD, which does not need to carry out model experiments. Next, we studied about a component-type mathematical model of hydrodynamic forces in maneuvering motion to comprehend the mechanism of the forces. In this research project, we carried out oblique towing tests of several ship models to understand the transitional characteristics of hydrodynamic forces. From the analysis of time histories of hydrodynamic forces by using the component-type mathematical model, we got the following concluding remarks.1. The cross flow drag component is a significant factor of the transitional effect. At the beginning of constant velocity in motion, the cross flow drag of the ship that has a rectangular cross section, reaches quickly to a steady state. On the other hand, the cross flow drag of more practical ship needs much time to be stead state.2. The transitional effect of the viscous lift component is more prominent at the bow rather than the stern. But the effect is very little in total hydrodynamic force.3. From the results described above, it seems to be possible to estimate roughly the hydrodynamic forces in steady state from the transitional characteristics in the oblique towing motion.