Droplet Breakup in Flow Past an Obstacle: A Capillary Instability Due to Permeability Variations
Author(s)Protière, S.; Bazant, Martin Z.; Weitz, D. A.; Stone, H. A.
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In multiphase flow in confined geometries an elementary event concerns the interaction of a droplet with an obstacle. As a model of this configuration we study the collision of a droplet with a circular post that spans a significant fraction of the cross-section of a microfluidic channel. We demonstrate that there exist conditions for which a drop moves completely around the obstacle without breaking, while for the same geometry but higher speeds the drop breaks. Therefore, we identify a critical value of the capillary number above which a drop will break. We explain the results with a one-dimensional model characterizing the flow in the narrow gaps on either side of the obstacle, which identifies a surface-tension–driven instability associated with a variation in the permeability in the flow direction. The model captures the major features of the experimental observations.
DepartmentMassachusetts Institute of Technology. Department of Chemical Engineering; Massachusetts Institute of Technology. Department of Mathematics
EPL (Europhysics Letters)
Institute of Physics Publishing
Protière, S. et al. “Droplet Breakup in Flow Past an Obstacle: A Capillary Instability Due to Permeability Variations.” EPL (Europhysics Letters) 92.5 (2010): 54002.
Author's final manuscript