Generation of small mono-disperse bubbles in axisymmetric T-junction: The role of swirl

The dynamics of micro-bubble formation in an axisymmetric T-junction for a gas-liquid system is analyzed. The approach adopted involves the creation of a tapering gas-liquid meniscus from which a steady gas ligament issues by the introduction of a coaxial swirl in the liquid stream. A simple and easy geometry (an axisymmetric T-junction) suffices to introduce the swirl and to stabilize the meniscus, leading to the formation of small monodisperse bubbles. Full three-dimensional simulations (3D) have also been conducted to show that, even when the liquid injection is not perfectly axisymmetric, the bubbles generated under conditions of some focusing swirl are distinctively smaller than bubbles created in the absence of swirl. In such cases, the bubbles, produced at the trail of the vortex axis, become a serendipitous tool to visualize the non-axisymmetrical behavior of the vortex core, as shown by the simulations. (C) 2011 American Institute of Physics. [doi:10.1063/1.3610384]