Hisaaki Maeda

Time-domain analyses of elastic response and second-order mooring force on a very large floating structure in irregular waves

Real sea areas where very large floating structures are installed are random wave fields. Then, it is necessary to analyze the responses in the time domain due to directional waves. There exist hydroelastic deflections and slow drift motions in the responses of VLFSs in ocean waves. However, it is very time consuming to solve the equations of motion in the time domain and obtain these responses due to directional waves. It is unnecessary to solve such equations in the time domain, if mooring forces can be turned into on equivalent linear system. In this paper, we analyze the time-series responses without solving the equations of motion in the time domain. And, the corresponding model tests in uni- and two-directional irregular waves are carried out. The present method is validated by comparisons between the analytical and measured results of time histories, and moreover, the analytical method of a slowly varying wave drift force is also validated.

Hydro-elastic response reduction system of a very large floating structure with wave energy absorption devices

A very large floating structure has hydro-elastic responses that are an elastic deformation and a slowly varying drift motion. Generally, a breakwater is established to reduce the responses. However, it is very difficult to construct it from a technical point of view and costs rise when the water depth increases. Therefore, it is necessary to develop the response reduction system for a very large floating structure even in open seas. In this paper a new hydro-elastic responses reduction system of a very large floating structure by using wave energy absorption devices has been proposed. The characteristics of hydro-elastic responses of a elastic structure with wave energy absorption devices were investigated both experimentally and numerically. This new system was proved effective in reduction of hydro-elastic responses of a very large floating structure. Two numerical analysis methods were developed to estimate hydro-elastic responses of a very large floating structure. The results obtained by these methods give a good agreement with the experiment results.