Agradecimentos: M.A.S.F. acknowledges CNPq for the receipt of his doctoral scholarship during this work. The authors also acknowledge the receipt of a financial support from Petrobras, under Grant no. 0050.0022719.06.4

Spatial void fraction measurements of a vertical upward air–water flow on the slug regime are made. The experimental technique uses simultaneously a contact needle and two single wire sensors. The data processing combines the information of both types of sensors. The liquid slug local void fractions...

Spatial void fraction measurements of a vertical upward air–water flow on the slug regime are made. The experimental technique uses simultaneously a contact needle and two single wire sensors. The data processing combines the information of both types of sensors. The liquid slug local void fractions along the radial and axial directions are estimated employing time and ensemble averages. The spatial void fraction along the axial direction disclosed two patterns, one associated to the pipe core and the other near the wall. The data is further processed to render the average void fraction along the radial and axial directions and the slug unit void fraction profile. Uncertainty analysis and data consistency tests are applied the check data reliability

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