RIASSUNTO
ABSTRACT
Wave added resistance has great influence on the rapidity and economy of ships, and it is one of the major issues that must be considered in the design of hull lines. In this paper, a panel method based on three dimensional potential flow theory is used to study the problem of wave added resistance. The time-domain motion responses of Wigely-III ship and S175 container ship in head waves are calculated by AQWA, and then the wave added resistances of two ships are obtained by near-field pressure integration method. By comparing the calculated results with the experimental data in literature, it is shown that the variation trend and peak value are in good agreement, and the accuracy and efficiency meet the research requirements. The present method provides an approach of satisfactory accuracy and efficiency to predict wave added resistance of ships voyaging in waves.
INTRODUCTION
When sailing in waves, the ship will have heave, pitch, roll and other motions, which will cause an increase in resistance comparing with that in calm water. Research shows that the magnitude of wave added resistance could reach 10% ∼ 30% of calm water resistance. With the increasing pressure of energy and environmental protection, IMO has proposed the EEDI formula of the newly built ships, which restricts the energy consumption standard of civil ships more strictly. Therefore, wave added resistance is one of the important factors that should be taken into account in ship's design and optimization stage.
Wave added resistance is the component of the steady second-order wave force in the longitudinal direction, which is essentially a nonlinear force. The calculation methods can be generally classified into two categories, namely far-field and near-field methods. The far-field method was firstly introduced by Maruo (1960), and is based on considerations of the diffracted and radiated wave energy and momentum flux at infinity, leading to the steady added resistance force by the total rate of momentum change. The first near-field method was proposed by Boese (1970), which directly integrate the steady second-order pressure acting on the wetted hull surface to obtain wave added resistance. At the initial stage, most of the calculation methods are based on strip theory. Faltinsen et al. (1980) calculated added wave resistance by integrating pressure on average wetted surface of ship hull based on strip method. Arribas (2007) produced a comparison of different methods for the added resistance by using strip theory. With the development of 3D potential flow theory and the improvement of computer performance, 3D time/frequency domain boundary element methods has been widely applied. For example, Liu et al. (2011) employed a 3D frequency domain panel method and a hybrid time domain Rankine source solver based on Green functions and a far-field approach to calculate wave added resistance. Park & Kim (2016) used Rankine source method to solve the motion responses of the ship in head waves, and used the near-field method to obtain wave added resistance, which achieved good prediction accuracy.