Detection of two-phase flow patterns using the recurrence network analysis of pressure drop fluctuations

The two-phase flow (water-air) occurring in the square minichannel (3 × 3 mm) has been analysed. In the minichannel it has been observed: flow of grouped isolated bubbles, flow of confined bubbles, flow of elongated bubbles, slugs flow and semi-annular flow. The time series of pressure drop fluctuations was analysed using the analyses of traditional recurrence quantification and recurrence network. The two coefficients: recurrence period density entropy and transitivity have been used for identification of differences between the dynamics of two-phase flow patterns. The algorithm which has been used normalizes the analysed time series before calculating the recurrence plots. Despite the neglect of quantitative signal characteristics the analysis of its dynamics allows us to identify the two-phase flow patterns. This confirms that this type of analysis can be used to identify the two-phase flow patterns in minichannels.