A model for slug length distribution in gas-liquid slug flow

Intermittent, or slug flow, is a very common occurrence in gas-liquid two-phase pipe flow. Usually slug flow is an undesirable flow pattern since the existence of long lumps of liquid slugs that move at high speed is unfavorable to gas-liquid transportation. Considerable efforts have been devoted to the prediction of the slug hydrodynamic characteristics, primarily by considering an average slug length and calculating average parameters. This approach is useful, and in many cases it is adequate for many engineering calculations. There are, however, cases where this information is not sufficient and much more detailed information concerning the slug length distribution, the mean slug length and the maximum possible slug length is essential. This work presents a model that is able to calculate the slug length distribution at any desired position along the pipe. The model assumes a random distribution at the inlet of the pipe and it calculates the increase or decrease in each individual slug length, including the disappearance of the short slugs, as they move downstream. The results of the calculation show that for the fully developed slug flow the mean slug length is about 1.5 times the minimum stable slug length and the maximum length is about 3 times the minimum stable slug length.