On three-dimensional solutions of drift forces and moments between two ships in waves

A far-field approach solving the lateral drift forces and moments between two ships in regular waves is adopted. The velocity potentials for diffraction and radiation based on a 3-D-source distribution technique are obtained. Using the Telste & Noblesse algorithm with a series expansion technique for the principal value integral solves the numerical solutions for corresponding Green functions and their derivatives. One pair of ship models is used for numerical calculations and a 2-D method based on the near-field approach is also included for comparisons. Generally the results obtained by the present technique indicate that the interaction effects between two ships have a profound influence on the drift forces and moments, and the direction of incident waves plays an important role. The results also show that the values predicted by the 2-D method are always very much overestimated because of the trapping energy between two ships. Therefore, the 3-D method prediction model developed here is regarded as more physically reasonable than the 2-D one.