Analysis on the signal features of differential pressure for air-water two phase flow in pipeline-riser system

Experimental investigation of air-water two phase flow was carried out in pipeline-riser system with 400 m long horizontal section. Four types of flow patterns was observed: severe slugging of type 1, severe slugging of type 1, transition flow, and stable flow. The differential pressure through the riser was analyzed in detail for the four different flow regimes including: changing rate, spectrum characteristics, and probability density distribution. The results showed that there are apparent differences in the changing rate of differential pressure for the four flow patterns. The differential pressure changing rate of transition flow is most dramatic while that of stable flow is most frequent. There exists obvious dominant frequencies for severe slugging, transition flow, and stable flow, but the amplitude of the dominant frequency for stable flow is obviously lower than others. The probability density distribution produced by the differential pressure is significantly different for the four flow regimes: unimodal distribution for severe slugging of type 1and stable flow, bimodal distribution for severe slugging of type 2, and most widely distribution for transition flow.