Direct Numerical Simulation of Liquid Films with Large Interfacial Deformation

Liquid films are important in many industrial applications, but also from a fundamental point of view, they are important two-phase flow systems. In this paper, we develop a sharp interface/level set method for the Direct Numerical Simulation (DNS) of liquid films with large interfacial deformations, and large density ratio between the liquid and the gas phase. We use the ghost fluid method to capture the interface motion without smoothing properties across it, and adopt a maximization scheme for the implicit treatment of the viscous term in the Navier–Stokes equations. Because liquid films have very low average depth compared to the distance between waves, several innovations are required to handle solving the equations on grid structures of high aspect ratio. Two-dimensional (2D) calculations for wavy films falling down a vertical wall are presented, and good agreement is found when numerical solutions are directly compared with the experiments of Nosoko et al. [1]. Some results are also presented for falling liquid films transitioning naturally from 2D to 3D surface wave structures demonstrating the potential of the method for 3D fully coupled two-phase liquid films simulations.