Berlin 2008 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 22: POSTERS Micro- and Nanofluidics
CPP 22.7: Poster
Wednesday, February 27, 2008, 16:00–18:30, Poster A
Two-dimensional gas-liquid two-phase flow in a microfluidic device — •Yasutaka Iwashita1, Ralf Seemann1,2, Christian Bahr1, and Stephan Herminghaus1 — 1MPI for Dynamics and Self-Organization, 37073 Göttingen, Germany — 2Experimental Physics, Saarland University, 66041 Saarbrücken, Germany
Monodisperse emulsions with a high volume fraction of the dispersed phase can be produced using step emulsification [1]: A quasi 2D-liquid stream of a dispersed phase surrounded by a continuous phase in a shallow channel is transformed into droplets at a topographic step by a Rayleigh-Plateau-type instability.
Here we replace the dispersed liquid by gas and study the gas-liquid two-phase flow in a similar microfluidic device. Due to the compressibility and lower viscosity of gas (more than 100 times smaller than liquid) the dynamics of the quasi 2D, two-phase flow is different from that of liquids. By observing the flow we found three characteristic flow structures: (i) gas-liquid co-flow at high pressure (or large flow rate) of gas, (ii) bubble generation at the T-junction of the shallow channel and (iii) liquid one-phase flow when the gas pressure is lower than the liquid pressure at the T-junction. We will show how these flow structures depend on the conditions (height of the shallow channel, interfacial tension, etc.), and explain the findings with a "simple" theoretical analysis.
[1] C. Priest, S. Herminghaus and R. Seemann, Appl. Phys. Lett. 88, 024106 (2006)