Session Ci - Vortex Dynamics.
ORAL session, Sunday, November 23
309, Moscone Center
For the first time, the evolution of the vortex ring structure created by a bursting bubble has been photographically studied and modeled. It has similarities to the structure created by an above-ground atomic test and by a water drop impacting a pool of still fluid. The bubble is situated on a thin, stationary layer of fluid on the top of a cylinder. Two upward-moving vortex rings with collinear axes are formed shortly after bubble rupture. The two rings leapfrog and then form a structure consisting of a vortex ring which sheds "lobes" of fluid which are sometimes similar in appearance to hairpin vortex loops. A two-dimensional point vortex computational model was created which produced images with resemblance to the physical structure. Both the experimental and computational results suggest that the lobes are rotational in at least some cases. The kinematics of the bubble film were also studied since the initial conditions of the vorticity are created when the bubble bursts. It was discovered that the edge of the film traces a spherical surface as it retracts, and that its velocity is not constant but greatest in the initial stages of retraction. This work was supported by NSERC Grant No. OGP004174 and the Central Research Fund of the University of Alberta.