Abstract

Prediction of hydrodynamic forces acting on a ship hull is important to predict ship manoeuvrability precisely. In this paper, SQCM (Source and Quasi Continuous vortex lattice Method) is introduced to predict lateral force and yawing moment acting on a ship hull representing the shape of the hull accurately. To represent flow field around the hull appropriately, free vortex models considering deformation of them are introduced. The purpose of this study is to investigate the applicability of the SQCM to the prediction of hydrodynamic forces acting on a ship hull in drift motion.

INTRODUCTION

To have a better understanding about manoeuvring performance of a ship at an initial design stage, prediction of hydrodynamic forces acting on a ship hull is important issue. There are three kinds of methods to obtain hydrodynamic coefficients to express the hydrodynamic forces such as captive model tests, approximate formulae with the parameters of principal dimensions of a ship based on existing data, and numerical calculation methods based on hydrodynamics.

Captive model tests can provide accurate data of hydrodynamic forces, but they require a lot of time and cost. Approximate formulae are simple calculation methods which can be used easily, but the estimation accuracy of the methods becomes poor if the hull shape of a target ship is different from mother data used to developed the approximate formulae. As the numerical calculation methods, CFD (Computational Fluid Dynamics) is available to predict the hydrodynamic forces by directly solving the Navier-Stokes equation numerically. However, it requires a lot of computational cost and time. As the other kinds of numerical calculation methods, panel method can also accurately describe the shape of a ship hull and predict the hydrodynamic forces. The SQCM (Source and Quasi Continuous vortex lattice Method) is one of the panel methods and it has been confirmed that the SQCM had good accuracy to calculate hydrodynamic force produced by a propeller.

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