The role of the difference in the densities of the contacting media of the drop impact in a deep fluid in the intrusion mode, when the kinetic energy of the droplet is less than the potential surface energy, is studied using high-speed video recording. The evolution and dynamics of the intrusion and vortex rings are assessed when a weak aqueous solution of potassium permanganate and ethanol merges with pure water and solutions of table salt.
A. Yu. Ilinykh (Sun,) studied this question.