Hydrodynamic Phenomenon and Its Effects in Large Scale Floating Structures

在这项研究中，首先，波浪载荷的分析方法的准确性，这已经在实验室中开发的首席调查员，讨论了通过与实验的半潜式模型与大量的柱连接的下船体。在数值模拟中发现了一个有趣的现象，即当入射波具有特定的方向和频率时，由大量密集分布的大直径圆柱组成的模型会产生驻波，并得到了实验的证实。比水平方向上的小得多。因此，通过将三维矩阵法与上述波浪载荷分析方法相结合，开发了包含刚体运动的竖向弹性变形分析方法，并通过与模型试验的比较证实了其高精度。从所得结果可以看出，在具有大量柱单元的大型半潜式平台的情况下，应考虑水弹性。另一方面，关于风，进行了风载荷的实验研究。利用东京大学土木工程系的全跨度模型风洞，对一大型半潜式平台模型进行了单元阻力和升力试验。特别是，在某些情况下，半潜式结构物和高波高的固体波浪表面的组合模型用于测量波浪存在对风荷载的影响。结果表明，风荷载并不小，特别是在上述组合模型的情况下，风荷载可能相当大，因此，进一步研究风对大型半潜式平台性能的影响具有重要意义。

In this study, first of all, the accuracy of the analysis method of wave load, which has been developed in the laboratory of the head investigator, was discussed by comparison with experiments of a model of semisubmersible with a large number of columns connected by lower hulls. An interesting phenomenon of generation of standing wave was found out in the numerical simulation by the above analysis method and confirmed by the experiments in the case where the incident wave has some particular direction and frequency for the model composed of densely allocated large number columns with large diameter.In the case of large scale semisubmersibles, the rigidity with respect to deformation in the vertical direction is, generally speaking, much smaller than that in the horizontal direction. Therefore, an analysis method for vertical elastic deformation including rigid motion was developed by combining the 3D-matrix method with the wave load analysis method mentioned above and the high accuracy was confirmed by comparison with experiments of a model. It can be said from the results obtained that hydroelasticity should be taken into account in the case of large scale semisubmersible with a large number of column elements.On the other hand, regarding wind, an experimental study on wind load was carried out. Using the wind tunnel for full span model test belonging to the department of Civil Engineering of the University of Tokyo, element-wise drag and lift foyces of a model of a large scale semisubmersible were measured. Especially, in some cases, combination models of the semisubmersible structure and a solid wave surface with high wave height were used to measure the effect of existence of waves on wind loads. The results showed that the wind load is not so small and may be considerably large especially, in the case of combined model mentioned above.Therefore, it is considered to be important to study further the effect of wind on behaviors of large scale semisubmersibles.