Interaction of a liquid flow around a micropillar with a gas jet

Elcock, D.; Jung, J.; Kuo, C.-J.; Amitay, M.; Peles, Y.
December 2011
Physics of Fluids;Dec2011, Vol. 23 Issue 12, p122001
Academic Journal
An experimental study was conducted to investigate two-phase flow characteristics resulting from gas jet injection into a 225 μm high by 1500 μm wide microchannel. The jet was injected from a 25 μm wide slit on the downstream side of a 150 μm diameter pillar. The liquid Reynolds number (Re = ρUD/μ) based on pillar diameter ranged from 100 to 700, and the average gas momentum coefficient (ρjetUjetAjet/ρmainUmainAref), defined as the ratio of gas momentum to liquid momentum, ranged from 1.6 × 10-5 to 3.368 × 10-1. Flow visualization, micro particle image velocimetry (μPIV), and micro particle tracing velocimetry (μPTV) were used to elucidate the two-phase flow patterns, liquid velocity field, and bubble dynamics. Two modes of gas jets were observed in which bubbles either formed and detached at the pillar or formed an attached ligament that sheared bubbles from its trailing edge. The modes were determined to be primarily Reynolds number dependent. Both modes were observed to positively affect turbulent kinetic energy in the microchannel. The momentum coefficient of the gas jet had the most significant effect at low Reynolds numbers, when bubble formation took place at the pillar.


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