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Air entrapment in droplets impacting the surface

 
: Ye, Qiaoyan; Tiedje, Oliver

Hilt, Michael (Chairman) ; Fédération d'Associations de Techniciens des Industries des Peintures, Vernis, Emaux et Encres d'Imprimerie de l'Europe Continentale -F.A.T.I.P.E.C.-; Gesellschaft Deutscher Chemiker -GDCh-, Frankfurt/Main; Gesellschaft Deutscher Chemiker -GDCh-, Fachgruppe Lackchemie; Verband der Ingenieure des Lack- und Farbenfaches; The Oil & Colour Chemists' Association -OCCA-:
New functions and sustainability - drivers for future coatings : European Technical Coatings Congress, 3-5 September 2014, Cologne, Germany
Frankfurt am Main, 2014
27 Folien
European Technical Coatings Congress (ETCC) <2, 2014, Cologne>
English
Conference Paper
Fraunhofer IPA ()
Lufteinschluss; Tropfen; surface; Oberfläche

Abstract
Air entrapment in droplets under impact onto a dry smooth solid surface was numerically investigated using three-dimensional computational domain with high-resolution grid. The study was focused on the drop spreading phase without splash and break-up. We present detailed numerical observations of the velocity and pressure distributions, as well as the initial air disc formed at the impact point. Results of numerical simulations indicate that thin air layer results from the direct contact between the droplet outline and the substrate. The maximum air disc is reached if the wetted contact line moves. The size of air disc and the release of air bubbles depend on material properties and application parameters. Parameter study was carried out. For viscous drop, the size of the entrapped air disc is inversely proportional to the surface tension of the fluid and increases with impact velocity and liquid viscosity. The entrapped bubbles release the drop during the oscillation of the drop spreading. Decreasing static contact angle will promote the release of air bubble from drop.

: http://publica.fraunhofer.de/documents/N-328042.html