Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 44: Micro- and Nanofluidics I
CPP 44.15: Vortrag
Donnerstag, 17. März 2011, 17:45–18:00, ZEU 160
Drop Impact on Free-Standing Surfactant Films — •Daniela Fell1, 2, Mordechai Sokuler1,2, Andreas N. Lembach2,3, Chuanjun Liu1,2, Elmar Bonaccurso2, Günter K. Auernhammer1, and Hans-Jürgen Butt1,2 — 1Max Planck Institute for Polymer Research, 55128 Mainz — 2Center of Smart Interfaces, 64287 Darmstadt — 3Institute of Fluid Mechanics and Aerodynamics, 64287 Darmstadt
We investigate the influence of drop composition on the drop’s behavior during impact. The drops of either water or aqueous surfactant solution had a diameter of (2.4 ± 0.4) mm and impacted with a velocity up to 1.3 m/s. As surfactants the anionic sodium dodecyl sulfate (SDS) and the cationic cetyl trimethyl ammonium bromide (CTAB) were used. Pure water drops impacting on surfactant films showed coalescence, bouncing, passing, partial bouncing, and partial passing. When surfactant was added to the drop, partial passing was suppressed and coalescence was replaced by (partial) bouncing.
We interpret the different phenomena based on the repulsive hydrodynamic force arising when the air has to flow out of the closing gap between the two liquid surfaces. This repulsion is influenced by the hydrodynamic boundary condition at the air-water interface. For a mobile interface represented by water drops impacting on surfactant films the outflow of air should be faster than for a no-slip boundary condition represented by both liquids containing surfactant. The boundary condition change from mobile to no-slip condition leads to stronger hydrodynamic repulsion in case of impacting surfactant drops.