The effect of oscillatory translational shear on viscous fingering in miscible fluids

Viscous fingering is an instability that results from the displacement of a more viscous fluid by a less viscous one in a narrow gap, such as between the two plates of a Hele-Shaw cell.  Previous studies showed that the fingering patterns are related to the interfacial structure in the thin dimension traversing the gap.  Here we study if the system can be stabilized against fingering by shearing the two plates with respect to one another.  Shearing the fluid in this way can reduce the viscosity contrast across the interface.  In our experiments, we inject fluid radially from a central hole in one plate while an oscillatory uniaxial translational shear is applied. We find that there is a delay in the instability onset and a suppression in finger length for fingers growing in the direction parallel to the shear as compared to those growing in the perpendicular direction.