Chemical Engineering Science, Vol.84, 100-106, 2012
Wetting effect on bubble shapes formed in a cylindrical T-junction
The study of forces acting inside a fluid or at the interfaces liquid/liquid, liquid/vapour or liquid/solid is very significant to improve the understanding of the multiphase flows in microdevices designed for material science applications such as pharmaceutical of food industries to name but a few. Even if the phenomena at the interfaces between the different phases are widely investigated, they continue to have a huge interest in microfluidics. This experimental study underlines the importance of wetting on air bubbles formed by a liquid/gas cross-flowing mechanism inside a glass cylindrical T-junction device. Experiments were performed by using various liquids as continuous phase that may provide different wetting behaviours. For typically small capillary numbers of the continuous shear stream, results give rise to the significant effect of the contact angle between the liquid and solid on the bubble size. Indeed, for a partially or a non-wetting behaviour, there are discrepancies between the measured bubble lengths and those predicted by Garstecki et al.'s model given for a completely wetting liquid/liquid or gas/liquid system. This can be explained by the non-uniform displacement of the contact line at the tube wall. (C) 2012 Elsevier Ltd. All rights reserved.