Experimental study of the effect of surfactants on the characteristics of waves in three-dimensional wave regimes

Effect of a surfactant Triton X-100 on three-dimensional wave regimes of the falling liquid film flow was experimentally studied. The shadow method and laser induced fluorescence measurements revealed that for surfactant concentrations at which complete suppression of wave motion is not observed, the flow characteristics at the three-dimensional wave regime differ from the characteristics of a pure water flow. Most likely, these differences are associated with differences in the structure of flows under the three-dimensional wave, which were revealed by simultaneous measurements of the thickness and volumetric measurements of the velocity in the wave at the initial section of the flow. For films with the surfactant concentration of 2000 mg/l, the capillary ripples in front of the three-dimensional wave are weakly expressed, there are no backflows, and transverse flows in the area of the capillary precursors are much weaker than in the case of pure water. (paper)