Low-frequency harbour oscillations

摘要

There are several papers concluding that the free long waves are generated to compensate the discontinuity of the forced long waves across the harbour (or channel) mouth. But the linear waves should be continuous across the mouth and the forcing terms in the free surface condition also should be continuous. Therefore, there is no reason for the forced waves to have discontinuity across the mouth. In the present paper, we re-analyze the problem of Bowers (1977) in more exact way and show that the numerical discontinuity of the forced waves comes from the Gibbs phenomenon of the Fourier analysis. Therefore this discontinuity has no physical meaning and do not generate the free long waves.