Experimental analysis of the bubble–slug transition in a flow generated by a T-junction in a minichannel with air/water and air/ethanol mixtures in conditions relevant to microgravity

We present an experimental study on the bubble–slug flow pattern transition which takes place in two-phase flows in microgravity related conditions. Two different sets of experiments were performed on ground with air/water and air/ethanol mixtures in a minichannel with an internal diameter of 1 mm. We address questions regarding the existence of a critical void fraction for the bubble–slug transition to occur. Experimental data are compared to the drift-flux and Suratman models predictions. We obtain results on the extension of applicability of these models for different boundary conditions.

► Bubble–slug flow pattern transition study in conditions relevant to microgravity. ► Experiments were performed on ground with a T-shaped bubble generator. ► Comparison between water/air and ethanol/air mixtures. ► Flow pattern map in terms of the gas and liquid superficial velocities. ► Confirmation of a critical void fraction associated to the flow pattern transition.