A linear three-dimensional frequency-domain numerical model for the prediction of ship motions in regular/irregular seaways

Linear three-dimensional frequency-domain singularity distribution methods have become a reliable tool for the prediction of ship motions in regular/irregular seaways. In this paper, an existing numerical model is extended to incorporate the non-potential roll damping into the original linear formulation-in an equivalent linearized form-and is estimated by the semi-empirical method due to Ikeda. In addition, the numerical model was extended to predict heave, pitch and roll motions in long crested irregular waves with ITTC spectrum in the two parameter form of the significant wave height and average wave period and for a range of wave headings. The accuracy of the developed numerical model has been validated by comparing the result with results available in the literature for the S-175 containership advancing at forward speed equivalent to Fn. = 0.275. Obtained results have shown satisfactory agreement with experimental data. In particular, the influence of accounting for the non-potential roll damping and the role it plays in predicting more realistic roll motions in regular beam seas and irregular oblique seas.