Capillary instability driven by a permeability gradient

ORAL

Abstract

Viscous fingering, the phenomenon associated with the Saffman- Taylor instability, occurs when a low viscosity fluid penetrates a fluid of higher viscosity. Surface tension generally acts to stabilize the interface of the two fluids. In this work, we study a new surface-tension-induced instability that is driven by a permeability gradient. The instability is even revealed when a fluid of higher viscosity penetrates a fluid of lower viscosity (stable in the Saffman-Taylor sense). This capillary instability is demonstrated in a microfluidic setup composed of two symmetric channels that linearly increase in width, rather than the traditional Hele-Shaw cell. The conditions necessary to achieve this instability are studied. In particular, we determined a critical capillary number below which the instability occurs. The effect of viscosity ratio and permeability gradient are also examined.

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Authors

  • Talal Al-Housseiny

    Department of Chemical and Biological Engineering, Princeton University

  • Jesus Hernandez

    Department of Physics, California State University at Northridge

  • Jeffrey Aristoff

    Department of Mechanical and Aerospace Engineering, Princeton University, MAE-Princeton University, Princeton University

  • Suzie Protiere

    CNRS - Institut Jean Le Rond d'Alembert, CNRS/IJLRA-Universite Paris 6

  • Howard A. Stone

    Department of Mechanical and Aerospace Engineering, Princeton University, Princeton University, Mechanical and Aerospace Engineering, Princeton University, Princeton University, Princeton, NJ, MAE-Princeton University, Princeton university