3-DIMENSIONAL TIDAL FLOW AROUND HEADLANDS

Field measurements of tidal flow around a headland indicate secondary circulation induced by flow curvature. The secondary flow, defined to be the flow in the plane normal to the direction of the vertically averaged current, is directed toward the headland near the bottom and seaward near the surface, consistent with theoretical predictions. The strength of the secondary flow varies from 5 to 15% of the streamwise flow. It is strongest when the water column is stratified because of both the enhanced shear of the streamwise flow and the reduced frictional damping of the secondary flow. The transverse exchange accomplished by the secondary flow significantly influences the structure of the streamwise flow, causing a broadening of the transverse shear and changing the horizontal and vertical distributions of momentum. It may also have a significant influence on horizontal dispersion in the vicinity of headlands.