Abstract
A vortex ring at an interface of the density stratified flow behaves complicatedly and plays an important role in entrainment. When the vortex ring ascends through the density interface, secondary vorticity is generated on the surface of the vortex ring not only by the discontinuity in velocity between inside and outside of the vortex ring, but also by the difference between the direction of the gravity force and the density gradient. In this study, we estimated theoretically newly generated secondary vorticity constituting a vortex sheet over the surface of the vortex ring and integrated it over the surface of the vortex ring. Then the vortex sheet is divided into many circular vortex filaments and the deformation of the vortex sheet was calculated by investigating the motion of the filaments. From this analysis, it is found that negative circulation consentrates on doubly piled parts around the surface of the original vortex ring and the calculated results agree well with the experimental observation.
