Slug velocity and liquid layer thickness before an abrupt contraction in horizontal gas-liquid flow

This work presents the results of an experimental investigation into the effects of an abrupt area contraction on the upstream gas-liquid intermittent flow; in particular, the slug velocity (the velocity of slugs as seen from a fixed observer) and the thickness of the liquid layer in the stratified region between two slugs were measured by means of optical probes just before the contraction, and compared with the values obtained in a straight pipe with the same inner diameter and under the same flow conditions. The superficial velocities of the liquid were from 0.6 and 0.9 m/s, while that of the gas ranged from 0.3 to 5 m/s. The results indicate that the abrupt contraction results in a substantial reduction of slug velocity, and in a growth of the liquid layer thickness.