Study on added resistance of a tanker in head waves at different drafts

In this study, added resistance was evaluated experimentally and numerically in four draft conditions: full load, ballast, and two intermediate conditions between the full load and ballast conditions. A series of towing-tank experiments for ship motion and added resistance in the four draft conditions was carried out in head sea conditions. The ship motion and added resistance were measured for the wavelength to ship length ratios of 0.4-2.0. In the numerical approach, two different seakeeping analyses were adopted: the strip method and Rankine panel method. For the strip method, analytical or empirical corrections were added in the short wave condition. The experimental and numerical results for the heave and pitch motions and the added resistance were compared for the four draft conditions. The numerical motion responses of both approaches showed good agreement with the experimental data. For the added resistance, the Rankine panel method showed reasonable results in all draft conditions. In contrast, the strip method showed poor results except in the full load condition. Based on the comparison of the experimental and numerical results, the potential application of the two numerical methods to various draft conditions was considered.