Influence of a soluble surfactant on the wave characteristics of a liquid film flow

Abstract

Abstract In this paper we present results of experimental investigation of the influence of soluble surfactant (Triton X-100) on wave characteristics of vertically falling liquid film in the range of film flow Reynolds number 25 < Re < 95. Shadowgraph technique is used to analyze wave patterns on the whole length of the test section (140 cm). Film thickness fields obtained with the help of high-speed Laser Induced Fluorescence (LIF) technique in two areas in the bottom part of test section allow analyzing statistical characteristics of the film flow. Expectedly, adding surfactant suppresses wave motion. For some surfactant concentrations the absence of waves is observed in the whole test section. For other concentrations the wave repetition rate decreases with distance from the liquid inlet. Analysis of spectral characteristics reveals that for water with some concentrations of surfactant, as for pure liquids, the steady-state three-dimensional wave regimes are observed. The characteristics in such flow regimes differ from the characteristics of pure water flow.