Formation of stratified flow and onset of slugging at a gas-liquid merging Y-junction

Abstract

The interface profile and the pressure distribution of a stratified flow and the critical conditions for slugging at a gas-liquid merging Y-junction were examined both experimentally and analytically. Air flow through a nearly horizontal channel, and water was introduced into the air stream through a slit at the bottom of the apparatus. The water layer thickness and the pressure distribution along the upper wall of the main channel were measured. The critical air velocity for the slugging was also obtained for a fixed water inlet velocity. The effects of the air-water inlet velocities, the channel inclination angle and the water injection angle were examined in this experiment. An analysis was performed under the assumption of two-dimensional irrotational inviscid flow. The Stokes`` inverse transformation technique was adopted to convert the real x-y plane to the x-ψ (stream function) plane; then the potential flow equation was solved numerically in the transformed plane to predict the interface profile and the pressure distribution along the flow direction, and the results were compared with the measurements. The water layer peak was observed near the merging point; this peak decreased and shifted downstream as the air velocity or the channel inclination angle was increased. However, the interface profile showed a tendency to merge into an equilibrium height far downstream for a fixed water inlet velocity and channel inclination. For a larger water injection angle, a secondary peak was observed at a small distance downstream of the primary peak. The upper wall pressure dropped sharply just after the merging point due to the air flow acceleration (caused by the water layer peak). Then the pressure recovered to an equilibrium value at the downstream where the pressure rise due to the air flow deceleration and the pressure drop by friction balanced. As the air velocity was increased, the small amplitude waves were induced downstream of the primary water layer pe...