Characteristics of film flow during transition to three-dimensional wave regimes

Results of experimental study of transition processes from two-dimensional to three-dimensional wave regimes for the case of isothermal falling liquid film are presented. Experiments were carried out using liquids with various physical properties in the range of Reynolds numbers 5 < Re < 100. It is shown that the process of transition to the three-dimensional wave motion is accompanied by formation of rivulets and that the downflow evolution of the rivulets usually has non-monotonic character. The statistical analysis of the 3D wave's characteristics allowed us to characterize in detail different scenarios of downflow evolution of 3D waves and to determine the regimes of fully developed steady-state 3D wave flow. Noticeable differences between natural and forced wave evolution have been observed for the relatively small Reynolds numbers whereas for the higher Reynolds numbers fast evolution of all investigated statistical characteristics with achievement of the steady-state 3D wave regimes of film flow occurs.