SHIP MOTIONS BY A THREE-DIMENSIONAL RANKINE PANEL METHOD

A Rankine Panel Method is presented for the solution of the complete three-dimensional steady and time-harmonic potential flows past ships advancing with a forward velocity. A new free-surface condition is derived, based on linearisation about the double-body flow and valid uniformly from low to high Froude numbers. Computations of the steady ship wave patterns reveal significant detail in the Kelvin wake significant distance downstream of the ship, permitted by the cubic order and zero numerical damping of the panel method. The wave pattern appears to be sensitive to the selection of the free-surface condition only for full ship forms. The heave and pitch hydrodynamic coefficients, exciting forces and motions of a Wigley and a Series-60 hull have been evaluated in head waves over a wide range of frequencies and speeds. A robust treatment is proposed of the m-terms which are found to be critical importance for the accurate solution of the problem. In all cases the agreement with experiments is very satisfactory indicating a significant improvement over strip theory, particularly in the cross-coupling and diagonal pitch damping coefficients.