Investigation of Global and Local Flow Details by a Fully Three-dimensional Seakeeping Method

A fully-three-dimensional Rankine panel method in the frequency domain is validated for local pressures, motions, and added resistance. Previous formulae for added resistance contained errors resulting in large differences to experiments. This has now been remedied. The method is linearized with respect to wave height. The steady flow contribution is captured completely by solving the fully nonlinear wave-resistance problem first and linearizing the seakeeping problem around this solution. The same grids on the hull are taken for both steady and seakeeping computation. On the free surface different grids are used, either following quasi-streamlined grids or rectangular grids with cut-outs for the hull. The results from the steady solution are interpolated on the new free-surface grid. The method is applied to various test cases. Motions are in good agreement with experiments, but this is also the case for strip method results. Local pressures, especially for shorter waves, are much better predicted than by strip method. The added resistance is sensitive to higher derivatives of the potential and a numerical differentiation of these terms may be preferable to using higher-order panels.