Investigation into the direct calculation of added wave resistance of ship in forward motion with reflection ratio correction

Abstract

Affected by the minimum power assessment requirements of the newbuilding energy efficiency design index (EEDI), added resistance of ships navigating in waves has been attracted more and more attention. By using the Green's function of three-dimensional translating pulsating source (3DTP), radiation/diffraction problems and ship motions are solved and good results are obtained. Based on these, the three-dimensional (3D) scattered energy approach to evaluate added wave resistance is proposed, which is combined with the radiated energy method and the Salvesen's weakly scattering assumption. It is reported in previous studies the computed added wave resistance is in reasonable agreement with experiment results on fine ship in medium wavelength waves. But for short-waves, the direct calculation cannot give precise result due to the limitation of the theory assumption. It is also question for long-waves case. A semi-empirical formula is proposed to correct the added wave resistance due to diffraction in short-waves. Considering the reflection attenuate phenomenon of waves with various wave length, a new approach with reflection ratio correction is hired in the formula. Finally, the modified formula is achieved that can be applied to directly calculate ship advancing in waves of various wavelength or full frequency range. With the comparison of calculation and model test results, the new correction method is verified and validated. It is also proved it fits not only for fine ship, but also for large blunt ship.