Parameter study of microdroplet formation by impact of millimetre-size droplets onto a liquid film

The objective of this work is to carry out an experimental investigation on the influence of different parameters such as liquid properties (viscosity and liquid-gas surface tension), impacting droplet properties (velocity v(i) and diameter d(i)) and the thickness of liquid film on the emission of airborne particles produced by the impact of millimetre-size droplets onto a liquid film. Our results show that in the variation range studied, the increase of v(i) and d(i) or the decrease in liquid film thickness produces an increase in the mean number of microdroplets emitted by impact in the size range 2-50 mu m. Furthermore, it was also observed that an increase in viscosity involves a steep decrease in the mean number of microdroplets emitted. These microdroplets may be produced by the fingers pinching of the crown formed during impact. In the case of low surface tension liquid, the formation of bubbles involves high production of droplets smaller than 15 mu m. The results presented here constitute a database of the micro-droplets produced to validate models of droplet impact outcomes. (C) 2009 Elsevier Ltd. All rights reserved.