Wavy Dynamics of Confined and Inclined Falling Liquid Films

We present direct numerical simulations of thin viscous films falling in inclined channel of constant relative confinement, η = 2. The two films with the same Kapitza number, Ka = 509.5, flow in a passive and quiescent atmosphere of air, in presence of gravity, with a suitable monochromatic perturbation, applied at the liquid-velocity inlets. The study is made for different values of liquid flow Reynolds number, Re as a control parameter defined in terms of Nusselt flat film solution. Any orientation of films other than vertical leads to symmetry breaking causing the waves to grow differently on both interfaces. Variations of film flow characteristics such as wave amplitude (h), streamwise velocity (u), and minimum occlusion distance (dmin) are examined with Re for both films. The oscillatory behavior of films ranging from progressive periodic to solitary waves with flow reversals is observed for different values of Re. These flow variations are subjected to suppression when the films undergo strong confinement. Suitable scaling law is reported for dmin as a function of Re for two different values of channel inclination.