CFD modeling of two-phase flow with surfactant by an arbitrary Lagrangian–Eulerian method

Abstract

The effects of surfactants on the motion and deformation of sinking and rising drops are studied numerically by employing the arbitrary Lagrangian-Eulerian (ALE) method. To describe the surfactant transfer in two-phase flow, the transport equations of the surfactant in the bulk fluid and the interface are solved in a coupled way which was developed in the commercial solver. The applicability of the numerical approach is verified by a series of benchmark tests and then employed to simulate the sinking drop contaminated by insoluble surfactant. The predicted drop motions and velocity profiles show good agreement with the experimental results from the literature, and the “stagnant cap” is found in the rear region, where the surface velocity nearly vanishes. Furthermore, the effects of the soluble surfactant on the drop rising in a straight tube are studied in detail, and the numerical results also agree well with the experimental data. It is found that the surfactant at the interface leads to the decrease of terminal velocity, especially in the transition region of drop shape. In addition, the Marangoni stress would inhibit the inner circulation of the drop and leads to immobilized behavior at the interface. The present method exhibits good accuracy and affordability, which can be easily used to solve the two-phase flow with surfactant.