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Multistructural and Multiscale Instability Characterization of Gas-Liquid Two-Phase Flow with MRA-CMESSE.
Qing-Ming Sun1,2, Qing-Chao Yu1, Di Ba1,3
1School of Mechanical and Electrical, Qiqihar University, Qiqihar 161006, China.
Entropy (Basel, Switzerland)
|May 4, 2026
Summary
We developed a new method, multi-resolution analysis with composite multiscale equiprobable symbolic sample entropy (MRA-CMESSE), to analyze gas-liquid flow instability. This method quantitatively shows how increased gas velocity enhances instability by shifting energy to smaller scales.
Area of Science:
- Fluid Dynamics
- Nonlinear Dynamics
- Complexity Science
Background:
- Characterizing gas-liquid flow instability is challenging due to complex interactions across multiple scales.
- Existing methods like multiscale sample entropy have limitations in robustness and scale analysis.
Purpose of the Study:
- To develop an integrated framework for analyzing gas-liquid flow instability from a multistructural and multiscale perspective.
- To quantitatively characterize instability in different gas-liquid flow patterns.
Main Methods:
- Developed and applied the multi-resolution analysis with composite multiscale equiprobable symbolic sample entropy (MRA-CMESSE) framework.
- Evaluated MRA-CMESSE's robustness against data length variations compared to other methods.
- Analyzed differential pressure time series from vertical air-water two-phase flow.
Main Results:
- MRA-CMESSE demonstrates superior robustness compared to existing multiscale entropy methods.
- Bubble flow exhibits the highest instability (energy spread, high complexity at small scales); slug flow is most stable (energy focused at large scales, low complexity).
- Increased superficial gas velocity shifts energy and complexity to meso- and micro-scales, driving instability.
Conclusions:
- The MRA-CMESSE framework provides a novel quantitative method for analyzing gas-liquid two-phase flow instability.
- Increased agitation at meso- and micro-scales is identified as the primary driver of flow instability.
- This approach strengthens the physical basis for monitoring and controlling industrial gas-liquid flow systems.
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