操縦性流体力の過渡特性に関する研究

国际海事组织制定的船舶操纵性暂行标准迫切需要在设计阶段对船舶操纵性进行预报。在这个预报研究项目中，我们测量了作用在船体上的水动力的过渡特性，并试图从过渡特性来估算稳态的水动力。首先，我们研究了一种估算模型船附加质量的方法，这对于分析运动中的船舶所受的水动力是必不可少的。在此基础上，提出了一种通过船模试验测量附加质量的简便方法，并绘制出了积木式船舶附加质量估算的快速图表。我们还开发了一种利用CFD估算附加质量的方法，该方法不需要进行模型试验。其次，我们研究了操纵运动中水动力的分段式数学模型，以了解水动力的作用机理。在本研究项目中，我们进行了几个船模的斜拖试验，以了解水动力的过渡特性。采用组件式数学模型对水动力时程进行分析，得出以下结论：1。横流阻力分量是影响过渡效应的重要因素。在恒速运动开始时，具有矩形截面的船舶横流阻力迅速达到稳定状态。另一方面，实际船舶的横流阻力需要很长的时间才能稳定下来。粘性升力分量的过渡效应在船头比船尾更为突出。但对总水动力的影响很小。根据上述结果，可以从斜拖运动的过渡特性粗略估计定常状态下的水动力。

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.