A Numerical Investigation of Three-dimensional Falling Liquid Films

TL;DR

This paper numerically investigates the evolution and transition of waves on three-dimensional falling liquid films using a hybrid interface tracking method, providing new insights into wave dynamics and validating forced wave simulations against benchmarks.

Contribution

It introduces a hybrid front-tracking/level-set numerical method for accurately simulating three-dimensional falling liquid films, addressing previous challenges in interface topology and mass conservation.

Findings

Natural waves transition from 2D to 3D disordered structures.

Forced wave simulations match existing 2D benchmark results.

The method effectively captures interface topology without numerical artifacts.

Abstract

The flow of thin liquid films on inclined or vertical surfaces is one of immense importance, with applications spanning many types of process industries, due to the increased mass and heat transfer brought about by the presence of waves on film surfaces. While extensive research has been carried out in this area, many outstanding questions remain due to the complexity of the problem - a result of the extremely large aspect ratio and the three-dimensional nature. In this study, the evolution process of both naturally forming and forced waves on these thin liquid films is numerically studied using a hybrid front-tracking/level-set hybrid method which has the advantage of a distinct and accurate capture of the interface topology without being affected by the issues of mass conservation, numerical diffusion or spurious interface profiles. The simulation is conducted on an infinite domain specification through the imposition of periodic boundary conditions at the film outlet. The obtained results show the growth, step-wise progression, and eventual transition of natural waves from the two-dimensional state to three-dimensional disordered structures. Finally, three-dimensional simulations of artificially forced waves are carried out while different parameters/features of these waves are compared with the existing two-dimensional benchmark cases in the literature with excellent agreement found. Keywords: falling films, thin films, solitary waves, three-dimension, forcing, interface tracking