Formation of Negative Buoyant Vortex Rings at an Orifice Opening
Josué Sznitman and Thomas Rösgen
Heavier than air, CO2-loaded negative buoyant vortex rings are generated at an orifice opening of variable diameter using a piston–cylinder apparatus and are ejected vertically upwards into ambient atmosphere. Ring formation is investigated using a non-invasive Background-Oriented Schlieren (BOS) visualization technique. Under the present experimental conditions, negative buoyant rings may exhibit a distinctive leading vortex ring with “pinch-off”, followed by a trailing jet. Further flow characteristics due to orifice size and negative buoyancy effects are inferred from the slug flow model for vortex ring formation, in particular through the use of a non-dimensional energy, and from an instantaneous ring Froude number.