Closed Basin Modes of a Dual Basin Harbour

摘要

Closed basin seiches have been studied in Port Kembla, Australia, a compound harbour comprising two basins linked by a narrow channel. Despite the irregular geometry, there are well defined closed basin resonances which may be excited by long waves incident on the harbour entrance. The March 2011 Japanese tsunami excited open-basin modes, but did not significantly excite closed-basin modes. This is attributed to the very low incident wave energy at those frequencies. While the direct forcing of a closed basin mode has been extensively studied, the indirect forcing via an independent open-basin mode found here has not been extensively studied. It was found that single basin modes are more readily excited than the higher dual basin harmonics and the role of the irregular geometry in inhibiting some modes is discussed. The non-linear generation of a higher frequency mode unrelated to the forcing mode is demonstrated.