ABSTRACT

This paper addresses the hydrodynamic interaction of ship-shaped hull sections in prescribed roll motion and also in transient roll-decay motion. The flow around 2-D hull-section with four different model geometries are studied using a Finite Volume Method (FVM) based numerical model, and the results from the FVM scheme are compared with experimental data and other numerical results. For the prescribed roll motion, the effects of different hull geometries and roll angle amplitudes on the moment histories and corresponding hydrodynamic coefficients are presented, and the highest amplitude of motion studied has been increased to 20 degrees. The relation between the hydrodynamic coefficients and the corresponding roll damping rate and frequency in the case of transient roll response for different hull geometries and different initial displacements is also discussed.

INTRODUCTION

Ship-shaped hulls have often been found to be subject to excessive roll motions that inhibit their use as a stable production platform. Bilge keels have been widely used as an effective and economic way of mitigating the roll motions, and their effectiveness lies in their ability to damp out roll motions over a range of frequencies. The performance of roll motion, in a conventional sense, is measured in terms of hydrodynamic added-mass and damping coefficients. (Vugts 1968) was the first to calculate the hydrodynamic coefficients for sharp-edged sections in roll motions and observed the importance of the viscous effect. The estimation of these coefficients through various numerical methods and validation through experiments has been the focus of research over the years, (Na et al. 2002; Wilson et al. 2006; Yeung et al. 1998; Yeung et al. 2000). The estimation of the damping coefficient on a non-conventional hull-section is investigated experimentally by (Yuck et al. 2003), where they found that the roll damping could increase significantly due to the hull geometry.

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