Measurement of Circumferential Liquid Film in Horizontal Annular Flow Based on PLIF and K-Means Clustering

The formation of the liquid film at the top of the pipe in horizontal gas–liquid annular flow is critical for safety and efficiency in industrial production. Therefore, investigating and predicting the circumferential distribution of the liquid film is of great importance. In this article, the advanced planar laser-induced fluorescence (PLIF) technique with high spatial-temporal resolution is employed to investigate the liquid film. First, based on the <tex-math notation="LaTeX">K </tex-math> -means clustering algorithm and the distance metric in red–green–blue (RGB) color spaces, a novel image segmentation method is developed to extract the liquid film thickness with higher accuracy. The proposed method enables precise observations of the circumferential liquid film distribution, thereby contributing to a comprehensive investigation into the impact of the superficial gas and liquid velocities on the thickness and asymmetry of the liquid film. Moreover, the influences of gas–liquid velocities and circumferential angles on wave amplitudes are studied, which reveals that larger waves are limited to reaching the sidewalls of the pipe. Finally, based on the modified Froude number and the circumferential angle, a prediction model for the circumferential liquid film thickness in horizontal annular flow is developed.