An apparatus has been constructed to study the formation and dynamics of vortex rings. The rings are formed in water by a momentary jet discharge downward into a glass tank from an orifice in a submerged plate. The necessary impulse is provided by a pressurized reservoir and is controlled by a fast programmable solenoid valve.
A particular turbulent vortex ring with a relatively thin core was chosen for detailed study. The velocity field of this ring was measured at numerous locations in the tank, using a two-channel laser-Doppler velocimeter with digital tracking electronics. Beamsplitting and frequency-shifting were accomplished by two partially-overlapping radial phase gratings driven by hysteresis-synchronous motors.
The main aim of the research was to verify the similarity properties of the turbulent vortex ring and to determine mean particle paths and mean vorticity contours in the appropriate nonsteady similarity coordinates x/t(1/4), r/t(1/4). Some novel pattern-recognition techniques were developed to overcome the problem of dispersion in the trajectories of individual vortices.
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Submitted by antoq on Tue, 11/18/2008 - 02:22.
