Added resistance of a SWATH ship in head waves

The objective of the present paper was to extend the well developed strip theory and nonlinear hydrodynamic force theory of a single ship to the prediction of the added resistance for a SWATH ship advancing in head waves. An experimental technique is also carried out to validate the theoretical results. Basically, the nonlinear theory used in this paper originates from that of a single ship, and the hydrodynamic interactions between two hull bodies are included in the calculations. Three basic assumptions are made: (1) the hull body is a ″weak scatterer,″ (2) the second order potential is small and can be neglected, and (3) ship motion is based on the linear strip theory. The results of the present study show that the previously developed nonlinear theory for a single ship may be applied to predict the added resistance of a seagoing SWATH ship. Hopefully, the technique developed here may offer some useful information to the naval architect in SWATH ship design.