Comparative study on the numerical reproduction of falling film hydrodynamics based on different surface tension models

Abstract

Computational fluid dynamics (CFD) modelling is extensively and successfully used for the reproduction of liquid film hydrodynamics. Surface tension significantly influences the numerical reproduction of falling liquid film flow. In this study, the hydrodynamics of the liquid film flow over a horizontal tube and a vertical plate is explored with different surface tension models. The results reveal that the neglect of surface tension leads to quantitative and qualitative distortions in the numerical simulation of the thin liquid film. Both continuum surface force (CSF) and continuum surface stress (CSS) models can produce the hydrodynamic behaviors of the falling film on the horizontal tube and the vertical plate, including pendant droplets, column necking or necking break, thickness of the film, vortex, liquid film detachment, as well as the values and trends of the velocity components. However, the CSF and CSS models produce different transient phase contours and streamlines, as well as different profiles of the time-averaged velocity components of the falling films on the horizontal tube and the vertical plate. Besides, there is no obvious difference between CSF and CSS in the perspective of time-averaged film thickness on a horizontal tube.