Research on the analysis of hydro-elastic behavior of a very large mobile offshore structure in waves and its anti-motion

主要研究了以下3个课题。水动力行为分析计算机程序的开发对大型海上移动结构的水弹性理论进行了回顾，并开发了计算机程序。此代码使用p-FFT方法，该方法可以在实际的CPU时间内处理大约100,000个水动力面板的数十种弹性模式。此外，为了简化结构数据的输入输出和弹性模态的计算，采用了通用的商业规范MSC NASTRAN和MSC PATRAN的组合。这些商业规范和水动力规范之间的接口也已开发。从理论方面看，规范的特点是保持了结构离散化与水动力离散化的一致性，从而满足了造波阻尼与模态阻尼之间的能量守恒。对计算机代码进行了验证，并对代码进行了详细的收敛性测试，发现代码具有足够的收敛性，可以进行全尺寸结构的计算。利用粘性阻尼的实验数据，对粘性阻尼的影响进行了研究。将数值结果与NIES的实验数据进行了比较，证实了数值结果具有足够的精度。建立了超大型海上移动结构的分析，总结了总体结果，提出了VLMOS的概念。利用这一概念对导航和发电进行了仿真。仿真结果表明，本文提出的方法对VLMOS的概念设计是有效的。

The following 3 topics have been mainly studied.1.Developement of a computer code for the analysis of hydrodynamic behaviorReview of the hydroelastic theory for a very large mobile offshore structure and the development of a computer code have been carried out. This code uses the p-FFT method, which enables to handle dozens of elastic modes with about 100,000 hydrodynamic panels in a practical CPU time. In addition, in order to simplify the input and output of the structural data and elastic modes computation, the combination of MSC NASTRAN and MSC PATRAN, which are popular commercial codes, is used. The interface between these commercial codes and the hydrodynamic code also has been developed. From the theoretical aspect, the code features that the consistency between the structural discretization and the hydrodynamic discretization is maintained so that the energy conservation between the wave making damping and the modal damping is satisfied.2.Validation of the computer codeA detailed convergence test of the code has been carried out and it is find that the code has enough convergence to carry out the computation of full scale structure. The effect of viscous damping has been investigated with the experimental data of the viscous damping. Comparisons between the numerical results and experimental data by NIES have been carried out, and it is confirmed that the numerical results have enough accuracy.3.Establishment of the analysis of the very large mobile offshore structureSummarizing overall results a concept of VLMOS has been presented. Using this concept for the simulation of navigation and electric power generation has been carried out. Through the simulation, it is confirmed that the methodology developed in this research is valid for conceptual design of VLMOS.