Performance Prediction of a Blunt Ship in Oblique Waves

Abstract

On prediction of ship performance in actual seas, it is important to estimate external forces acting on a ship. The predominant factor is added resistance in waves which reduces ship speed. Therefore, added resistance in waves is required to be calculated with accuracy. In addition, since a ship sails with a drift motion due to winds and waves, it is required to estimate hydrodynamic forces and moment due to drift motion.As ocean waves is characterized their irregularity which contains various frequency and direction component, it is required to estimate added resistance in oblique waves as well as in heading waves. In this paper, it is investigated by tank tests whether the calculation method on added resistance in heading waves is applied to that in oblique waves. Furthermore, hydrodynamic forces and moment due to drift motion is calculated with appending a term of drag for wing of a small aspect ratio. The effectiveness of the calculation methods is shown by estimating decrease of ship speed in actual seas.