Enhanced profile-preserving phase-field model of two-phase flow with surfactant interfacial transport and Marangoni effects

Abstract

Using a regularized delta function to distribute surfactant interfacial concentration can simplify the computation of the surface gradient operator ${\nabla }_s$, enabling the phase-field model to effectively simulate Marangoni flows involving surfactant transport. However, the exact conservation of total surfactant mass is compromised due to deviation from the equilibrium phase field profile, numerical diffusion, and mass non-conservation in each phase. To overcome these limitations, we have developed a new model for simulating two-phase flow with surfactant transport along the interface. This model employs a profile-preserving strategy to maintain the equilibrium interface profile, ensuring accurate calculation of the regularized delta function and improving surfactant mass conservation. Within the framework of the advective Cahn-Hilliard phase-field model, we utilize a regularized delta function with a reduced gradient to minimize numerical diffusion. Furthermore, we introduce a hybrid surface tension model that integrates the free-energy and the continuum-surface force models to mitigate spatial discretization errors, particularly in scenarios with high density and viscosity ratios. Verification tests demonstrate the model’s effectiveness in simulating surface diffusion on stationary and expanding drops, suppressing spurious currents, and capturing the deformation of a two-dimensional drop in shear flow. The results closely align with analytical solutions and previous numerical studies. Finally, we apply the model to investigate the contraction and oscillation dynamics of a surfactant-laden liquid filament, revealing the role of the Marangoni force in shaping filament behavior.