Fun with Fluid Columns. Erin Englert & Nate Villaume

Abstract

The boundary between two unmixable fluids is often unstable. In the columnar geometry of our two experiments, a viscous jet and a phase-rich polymer column, this instability results in pinching off -- the column beads off much like water dripping from a faucet. Until recently, it was presumed that this pinching occurred simultaneously along the entire column. However, it has now been suggested that this pinching occurs sequentially. It is proposed that the viscosity ratio of two fluids controls the velocity associated with the invading instability . We hope to measure the velocity of the propagating instability from both the polymer (static) and viscous jet (dynamic) experiments. Currently, we only have velocities for the viscous jet. These measurements are internally consistent, but do not agree with theory.