Influence of Elasticity on Fingering Instabilities

Constant viscosity elastic fluids known as Boger fluids are the ideal choice to investigate the role and influence of elasticity on interfacial flows and instabilities. In this contribution, we charecterize the pinching dynamics and extensional rheology response of model Boger fluids using dripping-onto-substrate (DoS) rheometry protocols, resulting in measurable viscoelastic effects even though elastic properties such as modulus and first normal difference are either below the resolution limit of torsional rheometers or a source of elastic instabilities. We utilize this charecterization to show how elasticity impacts fingering instabilities by visualizing flows in a Hele-Shaw cell and discuss the connections with other free surface flows and instabilities where viscoelasticity can alter pattern formation and evolution.