Experimental and Numerical Investigation on Gravity-Driven Film Flow over Triangular Corrugations

Liquid film flow over triangular corrugations is investigated by simulations and experiments. The volume of fluid (VOF) method is used to track the free surface between the liquid and gas in computational fluid dynamics (CFD) simulations. In the experiments, a sCMOS camera is applied to capture the film flow in a channel. The comparison of the results from three-dimensional (3-D) simulations and experiments shows good agreement. To validate the simulations quantitatively, two-dimensional (2-D) simulations are carried out and the velocity profiles in the liquid film flow field are compared with experimental results. With the validated model, a series of numerical investigations of liquid film flow over triangular corrugations are accomplished. Resonance between the free surface and the corrugations is found when the Reynolds number (Re) of the liquid flow reaches a certain value. When resonance occurs, the amplitude of the waves on the free surface gets the maximum but eddies in the troughs of the corrugations are suppressed. The steepness effect of the corrugations is also investigated. No relationship between the steepness and the resonance could be observed, but steeper corrugations can cause undulations with higher amplitude on the free surface in the low Re range. To investigate the surface tension effect, the inverse of Bond number is introduced. It is found that the inverse Bond number (Bo(-1)) has a direct relation to the resonance phenomenon. Film flow with a lower Bo(-1) value encounters the resonance at a lower Re value. Since the velocity component normal to the corrugated plate plays a significant role during the convection of mass transfer in film flow, the normal flow intensity is investigated. A local maximum of the normal flow intensity is found at the resonance point.