Evolution of Views on the Wavy Structure of a Liquid Film in Annular Dispersed Gas-Liquid Flow

The wavy structure of a liquid film sheared by high-velocity gas flow with droplet entrainment from the film surface has been investigated. The paper presents an analysis of methods for measuring the local fluid film thickness and a review of classical concepts of the wave hydrodynamics of annular dispersed flow obtained in early studies using rather crude methods. A systematic description of the structure, evolution, and interaction of waves of various types is given based on an analysis of high-resolution spatio-temporal records of film thickness obtained by laser-induced fluorescence. The results are compared with the results of recent experiments, and the necessity of revising some classical concepts is shown. Directions for further research are suggested.