ABSTRACT:

For the purpose of predicting strongly nonlinear hydrodynamic phenomena, a CIP-based Cartesian grid method has been developed and validated through a comparison with measured time series of the local pressure induced by the green-water impact and observed flows around the ship's bow. However, hydrodynamic forces such as the added-mass and damping coefficients in the radiation problem have not been validated. Recently we carried out the forced oscillation tests in heave and pitch using a newly-constructed apparatus, which provided reliable data on the radiation forces. Thus a comparison is made between these data and numerically computed results by means of a CIP-based Cartesian grid method, the results are analyzed and discussed. And the accuracy of numerical result, and further development to be done are discussed at the end of the paper.

INTRODUCTION

For strongly nonlinear ship-wave interaction problems, the CFD method is becoming popular these days. It can mainly be categorized into two approaches: the unstructured grid approach and the Cartesian grid approach. A CIP (constrained interpolation profile) algorithm, developed by Yabe et al. (2001) is one of the most popular Cartesian grid approaches. The critical advantage of using the Cartesian grid is that the numerical solution does not depend on the locations of the body boundary and the free surface. By using such grid, the numerical simulation of strongly nonlinear problems with complicated free surface deformation and violent body motion is more efficient and robust than conventional body fitted approaches. A CIP-scheme-based Cartesian grid method, named RIAM-CMEN (Research Institute for Applied Mechanics, Computation Method for Extremely Nonlinear hydrodynamics), which has been originally developed at RIAM, Kyushu University, is introduced and employed in this study. This numerical method will be called the "CIP-based Cartesian grid method" in the present paper from now on.

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