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O: Fachverband Oberflächenphysik

O 75: Focus Session: Wetting on Adaptive Substrates I (joint session CPP/DY/O)

O 75.5: Vortrag

Donnerstag, 21. März 2024, 10:45–11:00, H 0107

Wetting underneath droplets on an oily surface — •Shiva Moradimehr and Kirsten Harth — Fachbereich Technik, TH Brandenburg, Brandenburg a. d. Havel

When a liquid drop impacts on a smooth surface, a thin layer of air evolves between the drop and the surface. The drop deforms under the influence of the ambient air that needs to be squeezed out before the drop can touch the substrate. The actual air layer profile depends on the impact velocity, ambient gas, drop liquid as well as the deformability of the substrate. For small impact Weber number, the air film ruptures before drop rebound. The wetting front connecting the drop and layer liquids propagates at velocities of few meters per second.

We study the wetting front velocity for droplets impacting on hard substrates covered by thin oil layers using high-speed interferometry at oblique incidence. The impact velocity, viz. the thickness of the entrained air layer, and the oil layer properties are varied. Both a model for contact spreading on a thin film or an film-rupture based model are initial candidates to describe the wetting front propagation.

Keywords: thin film rupture; fluid mechanics; high-speed interferometry; wetting; thin fluid films