Soft Matter Seminar: “Detecting Local Pressure Gradients in Viscous Fingering Instability”

The Syracuse University Department of Physics Soft Matter group is pleased to welcome Savannah Gowen, Graduate Research at the University of Chicago for the talk, “Detecting Local Pressure Gradients in Viscous Fingering Instability.”

Fluid fingers form when a lower viscosity fluid penetrates a higher viscosity one within a confined geometry such as in the gap between two parallel circular glass plates. The elegant branching patterns that form are similar to branching structures we see in nature, and for that reason, this system has become iconic to the study of pattern formation. However, as these finger structures continue to grow their morphology is less well understood. For both miscible and immiscible fluid pairs the growth dynamics change after the instability onset, and global pattern features are governed by the viscosity ratio. Using a novel experimental technique, we observe a new length scale related to the penetration depth of local pressure gradients both behind and in front of the interface at late times. We characterize this length scale and show the surprising validity of a simple model which was previously proposed to describe late-time pattern growth.