Abstract:
The dynamics of the displacement of one fluid by another in porous media or Hele–Shaw
cells depends on the viscosity contrast due to the Saffman–Taylor instability. If the less
viscous fluid is displaced by the more viscous fluid, the interface is hydrodynamically
stable and, thus, fingering does not occur. Herein, we show experimentally the occurrence
of fingering for hydrodynamically stable displacement in a partially miscible system
using an aqueous two-phase system. Quantitative correlation between the interfacial
deformation and a proposed dimensionless number demonstrates that body force driven by
spinodal decomposition induces the fingering instability. Moreover, the fingering observed
in this study is completely different from previously reported fingering phenomena in
hydrodynamically stable displacement in immiscible and fully miscible systems.
