Numerical simulations of the stretching and relaxation dynamics of viscoelastic freestanding liquid films

Understanding the role of elasticity in the stretching and relaxation processes of freestanding liquid films is a key step in the study of two-phase systems such as foams and emulsions. This work employs numerical simulations based on the finite element method to investigate the dynamics of viscoelastic films underoging biaxial extensional deformation followed by relaxation. Two constitutive equations (Oldroyd-B and Giesekus) are employed to capture the effects of elasticity, viscosity, and capillarity. A parametric study is performed to assess the effects of Weissenberg-number-variations on elastic energy accumulation and film thickness evolution. Distinct behaviors are found for the two rheological models: the relaxation of Oldroyd-B films is characterized by an increase in thickness at the center, referred to as ‘elastic leveling’; in contrast, Giesekus films exhibit a decrease in thickness that we define ‘elastic anti-leveling’. Our results highlight the critical role of viscoelastic effects in governing the transient behavior of freestanding films beyond classical capillary-driven flow. • Viscoelastic films are studied through finite element simulations. • Films undergo biaxial extensional deformation followed by relaxation. • Two constitutive equations are considered: Oldroyd-B and Giesekus. • Relaxation of Oldroyd-B films is characterized by increase in thickness at center. • Giesekus films exhibit thickness decrease at center, referred to as anti-levelling.