Second-order steady forces on a ship advancing in waves

The nonlinear forces, including the ’mean drifting forces and added resistance, exerted on a ship advancing in regular waves are formulated in the paper. Neglecting the second-order potential, the first-order one is used to calculate the second-order forces which are expressed as products of the radiation potential, diffraction potential, the incident wave potential, and the ship motion response. Based on the well-developed strip theory, the first-order potentials of each ship section are derived by source distribution method and the related first-order ship motion responses are also obtained. Several wave headings and ship speeds are considered. Comparisons are made with other theoretical results and some experimental data and good agreements are generally obtained. It is also found that the second-order forces obtained based on the present strip theory are generally better than those obtained by other methods.