Flow pattern evolution of a nanoparticle suspension drop with water merging in the impact flow mode

The evolution of the substance transfer pattern at the initial stage of merging a drop of nanofluid — a suspension of iron oxide nanoparticles — with tap water was tracked using high-speed video recording for the first time. Experiments were performed in the impact mode, when the kinetic energy of the drop significantly exceeds its potential surface energy (PSE). During merging, the nanofluid drop disintegrates into thin trickles, traces of which form linear and mesh structures on the surface of the crown and cavity. The trickles pierce the walls of the cavity and penetrate into the thickness of the liquid, where they form an intermediate layer. The general geometry of the flow is consistent with the coalescing pattern of a drop of electrolyte — a dilute solution of potassium permanganate. The evolution of the structure over time was traced at the initial stage of drop merging.