RIASSUNTO
ABSTRACT
A time domain higher-order Rankine panel method is developed and applied for predicting the wave-induced motions of a ship navigating with a small drift angle in waves. As for the numerical procedure of solutions, the double-body flow accounting for the trailing vortices effect is first evaluated and then applied in the free surface and body surface boundary conditions of unsteady velocity potentials. The pressure equality Kutta condition is imposed at the trailing edge of the ship hull to generate the required circulation. Subsequently, the higherorder Rankine panel method, in which the physical variables are described by the quadratic B-spline basis function, is used for the evaluation of wave-induced motions and added resistance. By comparing the present numerical results with the experimental data, an acceptable agreement is achieved, and it is shown that even in head waves the small drift angle has a considerable effect on the lateral motions, but the effect on the added resistance is relatively small.
INTRODUCTION
For a ship navigating at sea, it may subject to winds, waves and currents, which not only affect the ship motions, but also lead to power loss and speed reduction. Moreover, the Marine Environment Protection Committee (MEPC) of International Maritime Organization (IMO) has now established the new regulations to constrain the arising greenhouse gas emissions from the perspective of an Energy Efficiency Design Index (EEDI). Therefore, an accurate prediction of added resistance of a ship sailing in waves is highly important and practical.
Existing approaches for studying added resistance can be classified into experimental method and numerical method. The former mainly relies on the model tests which proved to be most reliable, but costly and time consuming as well; the latter usually can be divided into two categories: the potential flow method which includes near field method using pressure integration and the far field method using momentum conservation; and the Computational Fluid Dynamics (CFD) method for viscos flow.