Numerical Simulation Of Liquid Film Flows On Uneven Walls

Liquid film flow on walls or in pipe widely exists in daily life and nature, and it hasbeen used as an efficient heat and mass transfer technology in various fields due to itsunique properties. The most important design factors for these devices are the thicknessand the flow rate of liquid film, which are the critical parameters affecting the heat andmass transfer characteristics. The wall which liquid film flows on usually has somespecial micro structure, so it is of great importance to research the liquid film flowcharacteristics on the uneven surface.In this paper, the simulation software Fluent is adopted. A CFD model oftwo-dimensional gas-liquid two-phase flow is established based on VOF method. Andthe liquid film flow characteristics on inclined flat wall and corrugated wall are analyzed.The surface tension and wall adhesion in the computational domain are considered, andthe flow media includes water, acetone and ethanol. The flow characteristics on flat walland corrugated wall are respectively discussed, and the influence of wall inclined angle isinvestigated. The film variation while the liquid viscosity and surface tension changes arestudied. The impact of liquid inlet flow rate on the liquid film flow distribution, film freesurface and the wall shear stress are also considered. The results indicate that the filmflow characteristics are determined by the combined function of the liquid flow rate andfluid properties, and vortex may exist on the recession of some wall structure. The size ofvortex is in correlation with the liquid flow rate.In addition, the liquid film flow characteristics on triangular and rectangular wallare studied and some air existed between the film and the two kinds structures is found,namely the vortex which affects the heat and mass transfer coefficient generated in thetriangular and rectangular structure. The variation of the wall structure size or liquid inletvelocity results in the change of the size and position of the vortex. The free surface ofliquid film on triangle wall changes regularly with the wall structure, while the variety offree surface on rectangle wall is not obvious.