Experimental study of entrainment vortex characteristic at steam-water interface of a water-submerged steam jet

Interfacial fluctuation and turbulent entrainment in the vapour-liquid mixing layer have great influence on heat and mass transfer in direct contact condensation. In this study, an ingenious experimental design was adopted to explore the characteristic microstructure at the steam-water interface of a water-submerged steam jet. Firstly, the periodic evolution process of large-scale two-phase coherent entrainment vortexes in the upper and lower steam-water turbulent mixing layers was captured. This process was divided into four stages: vortex formation, vortex growth, vortex pairing and vortex shedding. At the vortex growth stage, the central axial displacement of vortex was approximately linear with time, whereas the variation of vortex scale was nonlinear with time. Secondly, the periodic fluctuation of jet penetration length was caused by the pairing and shedding of periodic vortexes. Finally, the vortex formation process and distribution law of mixing layer thickness were analysed. The average scale of vortex blob at the pairing position was predicted and showed good agreement with the experimental data.