Examination of interfacial shape and onset of slugging of a stratified flow at a combining Y-junction

Abstract

The interface profile and the pressure distribution of a stratified flow and the critical conditions for slug formation at a combining Y-junction are examined experimentally. Air flows through the nearly horizontal channel, and water is introduced into the airstream through the bottom slit. The water-layer thickness and the pressure distribution along the upper wall of the main channel are measured. The critical air velocities for the slug formation are also measured for a range of water-inlet velocity conditions. The effects of the air-water-inlet velocities, the channel inclination angle, and the water-injection angle are studied in this experiment. Basically, the water layer shows a peak near the merging point and then approaches to an equilibrium level far downstream. At the larger water-injection angle, another water-layer peak is observed slightly downstream of the primary peak. The pressure drops sharply near the merging point because of the acceleration of the air flow and then gradually rises up to a certain level at the downstream where the pressure rise by the air flow deceleration and the pressure drop by the friction are balanced. The slugging occurs when the air velocity exceeds an interfacial instability condition. The critical air velocity decreases with the increase of the water-injection angle or the water-inlet velocity. An empirical criterion for slugging at a combining Y-junction is also proposed. (C) 1998 Elsevier Science Inc. All rights reserved.