On the density structure of far-wake vortices in a stratified fluid

An experimental investigation of the three-dimensional density structure of far-wake vortices generated by moving a sphere in a linear saline stratification has been carried out via conductivity measurements. These measurements were performed in the vortex cores along vertical and horizontal profiles to capture the three-dimensional nature of the vortices. We first present a simple model of an isolated vortex, the calculated internal density field of which has been confirmed by the conductivity measurements performed in both turbulent and laminar wakes. The time-dependent density structure is also described, as well as the decay of the density peak within the vortices. An identical density structure corresponding to an intensification of the background stratification has been identified for far-wake vortices originating from either laminar or turbulent near-wakes. This suggests that these vortices exhibit universal features of quasi two-component structures in stratified fluids, such as large-scale vortices commonly found in the ocean. (C) 2000 Elsevier Science B.V. All rights reserved.