Rescaled range permutation entropy: a method for quantifying the dynamical complexity of gas–liquid two-phase slug flow

Interconnected ordinal pattern complex network for characterizing the spatial coupling behavior of gas–liquid two-phase flow

“…Hence, plenty of researchers have shifted to experimental methods to investigate the dynamics of gas-liquid two-phase flows in various channels, such as vertical pipes, 6 horizontal pipes, 7 inclined pipes, 8 porous media, 9 fluidized bed, 10 and micro-fluidic chip. 11 To reveal the hidden fluid dynamics from the experimental observations, many data analysis tools, including time-frequency spectrum, 12 recurrence plot, 13 complex network, 14 nonlinear analysis, 15 multi-scale analysis, 16 and wavelet analysis, 17 have been applied, and various two-phase flow characteristics, such as flow pattern complexity, 18 flow pattern irreversibility, 19 flow pattern transition dynamics, 20 fluid multi-scale dynamics, 21 fluid stability, 22 and the flow pattern determinism 23 have been clarified. One inherent characteristic of a two-phase flow pattern is the spatial coupling behaviors of the two immiscible phases, which is a key factor for indicating the evolutionary dynamics of the gas-liquid two-phase flow patterns.…”