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

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 sur-factant in the bulk fluid and the interface are solved in a coupled way which was devel-oped 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.(c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

The impact of surfactants on the motion and deformation of sinking and rising drops is investigated using numerical simulations. The arbitrary Lagrangian-Eulerian (ALE) method is employed to accurately model the surfactant transfer in two-phase flow. The numerical results are validated against benchmark tests and experimental data, showing good agreement. The findings reveal that both insoluble and soluble surfactants significantly affect the behavior of the drops, including the decrease in terminal velocity and the inhibition of inner circulation.