NUMERICAL SIMULATION OF SECONDARY CIRCULATION IN THE LEE OF HEADLANDS

Abstract

The paper gives details of a study to refine and further develop a two-diirensional depth average numerical model to predict more accurately the eddy shedding features often observed in the lees of headlands. Details are given of the application of the model to Rattray Island, just east of Bowen, North Queensland, Australia, where the strong tidal currents flowing past the island give rise to separation and hydrodynamic circulation in the lee of the island. In the governing differential equations used to predict the secondary circulation, particular emphasis has been placed on the representation of the shear stresses associated with the free shear lateral mixing layer in the downstream wake of the headland. Use of an experimentally determined lateral velocity distribution in the shear layer, together with an eddy viscosity approach, have led to the use of a relatively simple turbulence model, including both free shear layer and bed generated turbulence. A comparison of the numerically predicted velocities with corresponding field measured results around Rattray Island has shown an encouraging agreement, although there were some differences. The main difference between both sets of results was that the vorticity strength of the secondary circulation predicted in the numerical model was noticeably less than that measured in the field.