Destabilization and dry-spot nucleation in thin liquid films on partially wetting substrates using a low-pressure air-jet

Abstract

The rupture of a thin liquid film on a partially wetting substrate can be initiated by external forces. In this manuscript we present experiments and numerical simulations of the effects of a laminar axisymmetric air-jet impinging on triethylene glycol films. We numerically calculate stagnation pressures and shear stress distributions that are used in a model for the thin liquid film dynamics. Experimentally, we distinguish three regimes: 1) the depressions made by low pressure air-jets level out, 2) for intermediate pressures a single dry-spot is nucleated that grows with a constant dewetting speed, whereas 3) for higher pressure air-jets the film is thinned and a large number of dry-spots nucleate, grow and leave a droplet pattern behind. In the third regime the dewetting speed was not independent of local film thickness. Numerical simulations show a qualitative agreement with the experimental observations.