Secondary circulation induced by flow curvature and Coriolis effects around headlands and islands

Previous studies have shown that flow curvature in river bends generates a secondary circulation in the plane normal to the mean flow direction. A similar circulation pattern is shown to exist in oceanic situations when flows are subject to curvature, mainly due to interaction with topographic features. However, it is shown that, due to differences between oceanic conditions and river bends, theory and prediction methods based on the assumptions for river bends are invalid for oceanic flows. Via scaling arguments based on the equations of motion, that include both the effects of flow curvature and the Coriolis force, parameters that govern the different flow regimes are identified. The maximum strength of the secondary flow is derived for each flow regime and is verified using a three-dimensional (3-D) numerical model applied to an idealized island. It is also shown that upwelling, due to the generation of secondary flow, occurs off the tips of the headland or island, and its influence can extend far downstream.