Flooding in vertical counter-current annular flow Original Research Article

The hydrodynamic characteristics of falling liquid films inside a vertical tube (50.8 mm ID and 244 cm high) with counter-current interfacial shear at the onset of flooding have been investigated experimentally. High speed video photography and a flow visualization technique were utilized to investigate the mechanisms involved in the initiation of the flooding phenomenon over a wide range of liquid film Reynolds number (ReL=Γ4/μ) from 1391 to 6584 at a distance of 150 cm from the liquid inlet. The present experimental data indicated neither the interfacial wave growth nor reversal in the wave propagation could be responsible for the initiation of flooding. Also the measured velocity profiles indicated only a slight reduction in liquid velocity within a narrow region very close to the gas–liquid interface, and no flow reversal in the liquid film at the measurement location.