Interfacial relaxation – Crucial for phase-field methods to capture low to high energy drop-film impacts

Abstract

Capturing the relaxation of a capillary interface towards its equilibrium profile is pivotal for accurate simulations of two-phase flow at high dynamics using the phase-field method.The present contribution suggests a methodological extension of the phase-field method necessary to cope which such highly dynamic two-phase flows. For validation, we use high quality time-resolved experimental data on drop impact on a thin liquid film and associated crown formation dynamics under conditions where the entire process stays axisymmetric. Such experimental data are missing in literature and provided by this contribution. Hereby, we suggest a challenging yet axisymmetric benchmark, which is especially useful for the advancement of numerical methods for two-phase flows at high dynamics.It has been found that a novel approach for the mixing energy coefficient is to be devised so as to account for interfacial capillarity and interfacial relaxation. Using the above-mentioned high-quality data on drop-film interaction, it has been demonstrated that adequate treatment of interfacial relaxation in the phase-field method is crucial to capture low to high energy drop-film impacts at a high level of accuracy.