Separation of a boundary jet in a rotating fluid

Abstract

A semi-infinite jet flows along a vertical wall in a rotating fluid, with the nose of the intrusion approaching a corner where the wall turns through an obtuse angle θ + 180°. The jet separates at the corner and flows into the interior if θ exceeds a critical θc, otherwise part of the jet continues around the corner and flows along the downstream segment of the wall. The separation criterion is computed using an inviscid and piecewise-uniform-vorticity model, with s denoting the ratio of the maximum ‘offshore’ to ‘inshore’ vorticity. The separation effect is demonstrated by a laboratory experiment in which a two-dimensional jet flows along the wall from a source. Average velocities are used to estimate s, and to make semi-quantitative comparisons of experimental and theoretical θc. This suggests that the separation mechanism is independent of local viscous forces, although the cumulative effect of lateral eddy stresses in the jet is important in establishing the value of s immediately upstream from the corner. We suggest that our barotropic separation mechanism is relevant to mesoscale oceanic coastal currents.