Frequency and development of slugs in a horizontal pipe at large liquid flows

The generation of slugs was studied for air–water flow in horizontal 0.0763 m and 0.095 m pipes. The emphasis was on high liquid rates (u_LS ? 0.5 m/s) for which slugs are formed close to the entry and the time intervals between slugs are stochastic. A “fully developed” slug flow is defined as consisting of slugs with different sizes interspersed in a stratified flow with a height slightly larger than the height, h₀, needed for a slug to be stable. Properties of this “fully developed” pattern are discussed. A correlation for the frequency of slugging is suggested, which describes our data as well as the data from other laboratories for a wide range of conditions. The possibility is explored that there is a further increase of slug length beyond the “fully developed” condition because slugs slowly overtake one another.