Fluctuation characteristics of gas-liquid two-phase slug flow in horizontal pipeline

Slug flow was a flow of long bubbles and liquid slugs alternating in space and time, and under flowing conditions, it is intermittent and unstable. The fluctuation characteristics of liquid holdup, pressure and differential pressure of slug flow were investigated in a 40 m long, 50 mm I.D. horizontal pipeline. At the same superficial liquid velocity, the liquid holdup of liquid film both decreased rapidly at first and then decreased slowly with the increase of superficial gas velocity, while the liquid holdup of liquid slug decreased slowly at first and then decreased rapidly. At the same superficial gas velocity, the liquid holdup of liquid slug and liquid film all increased with the increase of superficial liquid velocity. By statistical analysis, it was found that the probability density distribution of the liquid holdup was bimodal distribution. The high liquid holdup peak was in correspondence with liquid holdup of the slug body and the low liquid holdup peak with liquid holdup of the film. The liquid holdup which was in correspondence with the respective peaks of probability density function was consistent with the mean liquid holdup of smooth stratified film and liquid slug. Moreover, the distribution of pressure was unimodal distribution or bimodal distribution, depending on the number of slug units, and the differential pressure distribution was unimodal distribution.