Temporal and spatial evolution characteristics of two-phase flow pattern based on image texture analysis
In order to study the temporal and spatial evolution characteristics of gas-liquid two-phase flow structure,a high-speed dynamic camera was utilized to acquire the dynamic image information of seven typical gas-liquid two-phase flow patterns in vertical and inclined 30° upward pipes with the testing ranges of superficial water velocity 0.02—0.4 m·s-1 and superficial gas velocity 0.005—2.7 m·s-1.The gray level co-occurrence matrix(GLCM)was used to quantitatively characterize 2D information in the local neighborhood of image for analyzing flow pattern image features and the four time-varying characteristic parameter indices which represented image texture structures of different flow patterns were extracted.Then the transition of flow structure in the development process of flow patterns and calculated Lempel-Ziv sequence complexity of the four time-varying characteristic parameter indices were analyzed,and compared with the complexity measurement,fractal scale and recurrence plot determinism calculated by conductance fluctuating signals.The study showed that the dynamic parameter evolution trends of flow pattern image texture structure characteristics described the variation of different flow pattern structures and dynamics complexity,and the correlation index(COR)was more effective to reflect the complexity of flow pattern dynamics than others.It indicated that the proposed dynamic image analysis method was helpful to understanding the flow pattern temporal and spatial evolution characteristics and also was an effective approach to identifying the gas-liquid two-phase flow patterns.