Abstract:
The deformation of an initially circular miscible blob in a rectilinear displacement is
investigated numerically for porous media when the blob is more viscous than the
displacing fluid. We find in the parameter space spanned by the Péclet number and
log-mobility ratio the existence of a new lump-shaped instability zone between two
distinct regimes of comet and viscous fingering (VF) deformations. The more viscous
circular blob is destabilized by VF only over a finite window of log-mobility ratio,
contrary to the displacement of a more viscous finite slice with planar interfaces. This
difference is attributed to the initial curvature of the miscible blob.
