Numerical study on wave-induced motions and steady wave drift forces for ships in oblique waves

Abstract

This paper considers numerical predictions of wave-induced motions and steady wave drift forces for ships in oblique waves. The velocity potential around the ship is computed via a time domain Rankine panel method. Based on the computed velocity potential, the six degree of freedom wave-induced motions were computed and then the second order wave loads were evaluated using a near field method. An artificial soft spring system was employed to control horizontal ship motions. The steady longitudinal and transverse wave drift forces and the steady yaw moment were computed for the KVLCC2 tanker at zero forward speed and for the S-175 containership at constant forward speed. Predicted results generally compared favorably to published experimental measurements. A systematic analysis of the effects of the soft spring system on wave-induced motions and steady wave drift forces demonstrated that, although the increased stiffness of the system changed the corresponding motion response of the ships, a spring's influence was negligibly small if its stiffness was weak enough.