The complex liquid film behaviors at flooding in an inclined pipe were investigated with computational fluid dynamic (CFD) approaches. The liquid film behaviors included the dynamicwave characteristics before flooding and the transition of flow pattern when flooding happened. The influences of the surface tension and liquid viscosity were specially analyzed. Comparisons of the calculated velocity at the onset of flooding with the available experimental results showed a good agreement. The calculations verify that the fluctuation frequency and the liquid film thickness are almost unaffected by the superficial gas velocity until the flooding is triggered due to the Kelvin-Helmholtz instability. When flooding triggered at the superficial liquid velocity larger than 0.15 m·s

-1

the interfacial wave developed to slug flow

while it developed to entrainment flow when it was smaller than 0.08 m·s

-1

. The interfacial waves were more easily torn into tiny droplets with smaller surface tension

eventually evolving into the mist flow.When the liquid viscosity increases

the liquid film has a thicker holdup with more intensive fluctuations

and more likely developed to the slug flow.