Observation of the bubble-like morphology of atmospheric air plasma in two-phase flow of vaporizing water

The splitting and/or coalescing branched streamer network patterns are the most common settings of the atmospheric plasma. In this work, it is reported that a volumetric bubble cluster pattern can be realized in the interaction process of an atmospheric pressure diffuse plasma with a two-phase jet flow of superheated water. A new method using electric heating of a metallic tube filled with water is proposed to generate such a kind of vaporizing fluid. The plasma characteristics during the hydrodynamic process have been investigated by means of the high-speed Mach-Zehnder laser interferometry. The crucial feature of the morphology of plasmas, marked by the shifted fringes, has been enveloped with high contrast bright boundaries in both schlieren and shadowgraph photography, suggesting a critical phenomenon may exist in the heat and mass transfer process. The formation of the bubble-like morphology has induced higher electron density, and it is also found that the increase in the temperature during the jet flow and the increase in the discharge current are accompanied. The methodology exhibits the potential of applications relevant in the context of atmospheric diffuse plasma sources of high electron density and tunable chemistry of the neutral species.