ONSET OF SLUGGING IN HORIZONTAL GAS-LIQUID PIPE-FLOW

The onset of slugging in horizontal pipes has been analysed by a new approach. The relation between the appearance of waves on the stratified film, the formation of slugs and the transition to stable slug flow has been quantitatively examined. A new, necessary but not sufficient criterion for the transition to "stable" slug flow has been derived from an initial condition of slug growth. It reflects the well-known fact that waves of all kinds may form, even leading to liquid bridging of the pipe, but that the resulting slugs decay over a wide range of flow rates. In general, for slug flow to develop, an unstable film flow situation with waves is necessary, in addition to a condition allowing slugs, once formed, to grow initially. It is further shown, by comparisons with large-scale, high-pressure data from the SINTEF Two-phase Flow Laboratory, that this criterion for slug growth is the more restrictive, and may in practice be applied alone for the transitions from stratified or annular flow to slug flow, or even to dispersed bubble flow for high-pressure systems.