Model for long-period oscillations in a harbour induced by incident wave groups

A numerical model based on the radiation stress induced by multidirectional irregular waves is proposed to estimate the long-period oscillations in a harbour due to bound long waves associated with incident short-wave groups. The model is compared with the Boussinesq equation model and is applied to a large-sized harbour in the field. The agreement in both cases is found to be satisfactory. Using the proposed model and Boussinesq model, the long waves in a harbour are further computed taking into consideration the coexisting free long waves with bound long waves as incident waves. The results indicate that the long-period oscillations in a harbour are largely influenced by the presence of the free long waves depending on the phase difference between the free and bound long waves near the harbour entrance. Field validation of the model for Kashima port is also discussed.