Numerical Simulation of a Liquid Film Driven by Turbulent Gas Flow in a Flat Minichannel

The liquid film driven by a turbulent gas flow in a flat minichannel under conditions of drop entrainment is investigated using a two-dimensional numerical model which employs a coupled volume of fluid and level-set (CVOFLS) method for interface capturing and the large eddy simulation (LES) approach with the Smagorinsky model to resolve turbulence. The results confirm that the transition from large-scale ducts to minichannels leads to a significant suppression of fast ripple waves on the rear slopes of disturbance waves, consistent with previous findings. However, the use of LES enables the resolution of these small-amplitude waves, revealing their increased frequency in minichannels. The analysis of the Q-criterion for vortex cores demonstrates that the generation of both initial waves near the liquid inlet and ripple waves on disturbance waves is driven by small-scale eddies in the gas phase. Furthermore, the model predicts the existence of vortical flow within the liquid phase of the disturbance wave itself and near the liquid inlet, which promotes the formation of ripple waves and initial waves, respectively. Thus, a qualitative similarity was observed between the formation of initial waves near the liquid inlet and the generation of ripple waves on the disturbance wave.