Two-wave structure of liquid film and wave interrelation in annular gas-liquid flow with and without entrainment

The wavy structure of liquid film in downward annular gas-liquid flow with and without liquid entrainment is examined for a wide range of gas velocities using high-speed laser-induced fluorescence technique. It is shown that the wavy structure is always represented by two types of waves, long-lived and short-lived waves with the latter always generated at the back slopes of the long-lived waves. Main regularities of short-lived wave generation and evolution are also described.