Abstract Hydrodynamic analysis of a moored semi-submersible type offshore wind platform has been carried out. Three methods are used in this study. The first method is the wave tank experiment with a 1/50 scale model which is carried out in the towing tank of RIAM, Kyushu University. Wind is not considered in the experiment and the mooring system is approximated by a spring system. The second method is the CFD simulation, which is performed by using our in-house research code RIAM-CMEN. This code is a based on a multi-phase Navier- Stokes solver for prediction of strongly nonlinear wave and wind loads on a floating body in rough sea conditions. The third method is a potential flow based numerical model, in which hydrodynamic loads on the floater are solved by the potential flow theory, the mooring lines by the catenary theory, and the aerodynamic loads on the wind turbine by the blade element momentum theory. This method is used as a practical analysis tool for parametric study. In this paper, numerical results are compared to the experimental data and discussions on these analysis methods are presented.

ABSTRACT: The particle method (Moving Particle Semi-implicit method) is applied to violent free surface problems on marine engineering. The sloshing on very shallow depth condition and the very large motion of floating body with water invasion in waves are simulated successfully with it. These results show realistic behavior. INTRODUCTION After recent tragic losses of ships, many researchers have studied about the ship's damage stability and deck wetness. In these studies, they have always pointed out that behavior of water on the deck is very important. However violent free surface flow and dynamic effect of flow have hardly been considered. Almost studies of damage stability are stand on the quasi-static assumption about the behavior of water motion on the inner deck of ships. The deck wetness and the green water load acting on the structure have been treated with model experiments. In spite of an increase of computational resources in recent years, there has hardly been direct numerical simulation of these phenomena with CFD(Computational Fluid Dynamics) techniques. The reason of this exists as a difficulty in handling the violent free surface flow like fragmentation of fluid. Then VOF(Volume of Fluid Method) and its refined methods which use space fixed grid system has been used in several past studies. These methods are effective in handling violent free surface flow, but they include some of problems like numerical diffusion of free surface, stair effect, robustness of calculation and so on. Another difficulties of numerical simulation about problems exist in handling very large motion of boundary like the capsized hull. BEM(Boundary Element Method) with ALE(Arbitrary Lagrangian and Eulerian) grid has been used in researches of the numerical wave tank to simulate motion of floating body. However it is difficult to handle breaking waves, damaged hull's opening, etc. even if using ALE grid.