To discuss the relation between complexity measures extracted from time series and flow pattern transition in gas-liquid two-phase flow, this paper analyzes the recognition capability of three complexity measures, including Lempel-Ziv complexity, spectral entropy and approximate entropy to different signals, such as periodic signal, stochastic signal, mixed stochastic signal and chaotic signal, and then the paper discusses the influence of the length of time series to the algorithms of the three complexity measures. Based on the above studies, we extracted the three complexity measures from eighty conductance fluctuating signals of gas-liquid two phase flow in vertical upward pipe. The results indicate that the three complexity measures are sensitive to the flow pattern transition in gas-liquid two-phase flow. By analyzing the rules of three complexity measures with the changes of gas-liquid two-phase flow parameters, we can get the dynamics structure inversion characters of gas-liquid two-phase flow, and they provide an efficient, supplementary diagnostic tool to reveal the flow pattern transition mechanism of gas-liquid two-phase flow.
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