In order to study the influence of gas flow rate on flow structure

interface motion of counter-current gas-liquid flow over structured packing surface

a CFD model based on detached eddy simulation(DES)and volume of fluid(VOF)method was developed.Explicit interpolation scheme was used for the VOF formulations

and the Geo-Reconstruct method was chosen as the volume fraction discretization scheme.Structured curvilinear grids were generated for the whole fluid domain and locally refined to ensure that at least 10 grid points were within the liquid film.When F factor was low(F≤1.354 Pa0.5)

the distribution of free-surface and its velocity component vy were periodic

and the fluctuation amplitude was almost uniform.Along the free-surface all values of vy were negative.As F=3.386 Pa0.5

fluctuation of free-surface appeared to be disturbed

while the distribution of vy kept periodic

and at the lower edge of liquid waves vy>0.As F=5.418 Pa0.5

back mixing of liquid phase appeared

recirculation regions were formed in both phases and evolved with the liquid back mixing process

and the liquid film could wholly move upward in some concaves of solid surface.As F≥6.772 Pa0.5

dry patch was formed at the lower part of packing region and no liquid could flow out from the bottom outlet.With the increment of F factor

both liquid holdup and effective interfacial area increased first and then decreased.