The two-dimensional flow oscillations of a fluid in a spindle-shaped basin; application to Port Kembla Outer Harbour, N. S. W., Australia

Abstract

Port Kembla Outer Harbour has a history of severe ranging during storm activity, and hence a knowledge of its resonant behaviour is a necessary requirement towards understanding the cause of the range action. The Harbour has been shown to be suitably approximated by a spindle shape, which is the name given by Hidaka (1931) to a basin whose surface perimeter is defined as the intersection of two confocal parabolae. In this paper Hidaka's results are enlarged, more basic harmonics being found. These are then applied to the Outer Harbour which is assumed to be excited by a fully formed clapotis with an antinode at the entrance. The two particular harmonics which are most likely to be excited are found to have the same period of 153 sec. Experimental evidence has given long wave periods in the Harbour as 150 and 160 sec. The resonant mode corresponding to a period of 54 sec is found to have a large amplification factor at the entrance to the Inner Harbour, and this may be compared with model study results where at 56-58 sec the range action is greatest.