Formation of a Floating-Up Vortex during the Merging of an Ethanol Droplet with Water in the Intrusive Mode

The evolution of the pattern of a drop of a 95% ethanol aqueous solution dyed brilliant green merging with water is traced using a high-speed video recording. In the traditional sequence of flows recorded in the intrusive mode, including the inflow of a drop into the liquid bulk with the formation of a lenticular intrusion, the delayed formation, development, collapse of the cavity, and the transformation of the intrusion into a plunging ring vortex, a new type of vortex ring is observed in the pattern of the merger of a drop of a lighter liquid being mixed. When the cavity maximal depth is reached, a compact volume containing drop matter is separated from the center of the pointed bottom of the cavity into the liquid bulk. The gradually submerging volume transforms into a small annular vortex, which, having reached its maximum depth, stops and forms a compact secondary intrusion of a cylindrical shape. Next, the intrusion, in which the lighter liquid of the drop is partially preserved, begins to float up and gradually transforms into a new ring vortex. The rising vortex leaves a cylindrical trace in the target liquid with a shell colored by the drop pigment. The diameter of the vortex gradually increases, and the trace takes on a bottle-shaped shape.