Spreading rate of a toroidal air bubble in water

The rise of a toroidal bubble in water obtained by injecting a pulsed jet of air into the water through a nozzle vertically upwards has been experimentally investigated. It was found that, despite the decrease in the cross-section of the toroidal bubble during the ascent, its radius grows linearly depending on the distance traveled, as in the case of self-similar vortex rings. The coefficient of expansion of the bubble at different volumes of injected air is determined. A comparison was made with toroidal bubbles obtained when balloons burst under water. A qualitative explanation of the observed differences is given.