Simulation of extensional deformation of a drop with an elastoviscoplastic interface

A numerical implementation of two-phase flow of Newtonian fluids with a non-linear viscoelastic interface is validated and applied to the case of uniaxial extension of a drop in a matrix fluid.After fitting the intrinsic viscoelastic stress-strain behavior of interfaces in shear to experimental results from the literature, the influence of interfacial rheology on the drop shape and interfacial stress is investigated. It is found that the drop shape is not significantly influenced by the viscoelastic properties of the interface if the interfacial viscoelastic stress, interfacial tension, and bulk viscous stress are of the same order of magnitude. However, the interface develops distinct stress profiles for varying interfacial viscoelastic properties. For the case of interfacial viscoelastic stress being larger than interfacial tension and bulk viscous stress, the simulations become unstable due to buckling of the interface caused by compressive stresses at the drop tip.