(195k) Interfacial Flows and Instabilities of Boger Fluids

Constant viscosity, but finite elasticity make Boger fluids an ideal choice for investigation of the role and influence of elasticity on interfacial flows and instabilities. In this contribution, we examine the pinching dynamics and extensional rheology response of model Boger fluids using dripping-onto-substrate (DoS) rheometry protocols, showing measurable viscoelastic effects even though elastic properties like modulus and first normal difference are either below the resolution limit of torsional rheometers or source of elastic instabilities. We thereafter show how elasticity influences fingering instability by visualizing flows within Hele-Shaw cell, and discuss the connections with other free surface flows and instabilities where viscoelasticity can influence pattern formation and evolution.