Asymmetric flow and mass transfer of twin-liquid films

Twin-liquid films are a combination of wall-bounded films and confined free films. The asymmetric flow is investigated with the VOF method. A new integration algorithm is developed for interfacial mass transfer (Pe=8400) with the subgrid-scale model [1]. Due to the dynamic balance of the surface tension and the spanwise inertia force, periodic interface oscillation at the lower edge of the window is observed. Then the capillary waves in the window become asymmetric, which induces different flux distributions on two sides of the lower wall, accompanied by large waves and vortices. The vortices extrude a scalar plume (local high concentration liquid) from the interface into the liquid bulk and roll it up once or twice in a reverse direction, significantly promoting the mixing and diffusion of scalar in the liquid bulk. As a result, the local mass transfer rate can be enhanced by 100%∼400% on the lower wall.