Two-phase flow pattern transition behaviors on experimental established ordinal pattern networks

Identifying the flow pattern transition dynamics is a fundamental challenge in modeling a two-phase flow system. In this paper, we investigate the gas–liquid two-phase flow pattern transition behaviors with analyzing the topology structures of the experimental established gas–liquid two-phase flow complex networks. First, we carry out a series of gas–liquid two-phase flow experiments in a vertical 50 mm inner diameter pipe. During the experiments, the two-phase flow fluctuation signals are collected and used to establish the ordinal pattern complex networks, which represent different flow patterns. Then, we employ a K-core decomposition method to identify the hierarchical structures of our established flow pattern networks. We find that the decay rate of the K-core size is sensitive to the flow conditions and can be a potential metric for identifying the flow pattern transitions. Additionally, we analyze the network homology persistence, which indicates the loop structures in the flow pattern networks. The persistence indexes—maximum persistence and persistence entropy—are used to investigate the flow pattern oscillatory behaviors along with the flow pattern transitions. This research provides a novel way for investigating the flow pattern transition behaviors of a gas–liquid two-phase flow system, which are expected to be applicable in other complex fluid systems.