Prediction of Wave Forces on a Ship Running in Following Waves with Very Low Encounter Frequency

Abstract

A theoretical method is proposed for computing the wave forces on a ship running in the following oblique waves with very low encounter frequency. It incorporates, in addition to the Froude-Krylov forces, all the terms up to the lowest order of magnitude with respect to the disturbance of the incident waves. They include the interaction effect between the stationary waves generated when the ship running on a calm water and the disturbed incident waves.
Several examples of numerical results by the method are presented to test its validity, for example, for predicting the wave yaw moment which was found by Motora et al. to bring about broaching-to phenomenon when it exceeds the course keeping ability of the ship given by the rudder action. The results show that the method proposed is better than the Froude-Krylov assumption for describing the relation between the wave force magnitude and the location of the incident waves relative to the hull.