ABSTRACT

Numerical simulation and experiment of strongly nonlinear ship-wave interactions are carried out for validation of our CIP based Cartesian grid method. In this paper, we describe the results on a two-dimensional case. The laboratory experiment is carried out on a box-type floating body. A forced heaving test is first performed and then tests on freely moving body in regular waves are made. Our research interest is focused on the strongly nonlinear interactions in which water on deck phenomena may occur and the hydrodynamic loads due to the green water may have important influence on the result. The numerical simulations are conducted on the experimental condition and good comparisons are obtained on both the forced oscillation case and the wave-body interaction case.

INTRODUCTION

The Cartesian grid approach to predict hydrodynamic loads in strongly nonlinear ship-wave interactions has been developed for years in RIAM, Kyushu University. Two-dimensional development and three-dimensional development of the code have been presented in previous papers (Hu and Kashiwagi, 2004 and Hu et al, 2005). The CIP (Constrained Interpolation Profile, Yabe et al. 2000) algorithm is adopted as the base scheme. The Cartesian grid is used for that it does not depend on the body boundary and the free surface. Then the computation of the strongly nonlinear problem, which may require treatment of both complicated free surface deformation and violent body motion, can be more efficient and robust than conventional body fitted approach.

The wave-body interaction problem in our numerical model is treated as a multiphase problem, which includes a liquid phase (water), a gas phase (air) and a solid phase (floating body). A CIP based finite difference calculation is carried out in a Cartesian grid that covers the whole computation domain. The free surface and the body boundary are treated as immersed interfaces.

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