Some aspects of interaction between three-dimensional and two-dimensional waves on vertically falling liquid films

The results of the experimental investigation into regularities of interaction of solitary three-dimensional waves with regular two-dimensional waves on vertically falling liquid films are reported. The film falling down over the plate surface was formed using a slit dispenser with a controlled gap width. A vertically mounted optical glass plate was used as the working section. Two-dimensional waves with various frequencies were excited by harmonic modulation of the liquid flow rate at the input into the dispensing section of the working section. The solitary three-dimensional wave was excited by a short shot 10-20 ms long of the jet of the working liquid in the upper part of the film flow. To investigate the dynamics of interaction of the waves with a high spatial and temporal resolution, a high-speed system for diagnostics of the flow by laser-induced fluorescence (LIF) was used. At lower excitation energies, an increase in the amplitude of the three-dimensional wave was observed, while at higher excitation energies, a decrease in the amplitude towards its magnitude in the steady-state was observed.