This paper aims at investigating the effect of the rough gas diffusion layer (GDL)on liquid water transport behaviors in gas channels (GCs)employing the volume of fluid (VOF)in the commercial CFD package

FLUENT 6.3.26.It is found that the liquid water on the hydrophilic rough GDL tends to spread along the corner and presents as a water film with the concave surface

with many holes in the GDL covered by the liquid water

whereas the liquid water on hydrophobic rough GDL presents as the water droplet which covers less holes and can be easily drained out of the GC

indicating that a hydrophobic GDL surface is desirable in PEMFCs.Simulations then focus on investigating the effects of the rough hydrophobic GDL on the liquid water transport behaviors in GCs.The simulation results show that the droplet is inclined to form the Cassie droplet on the rough GDL surface.The water droplet is easier to be drained out of the GC with the rough GDL surface.The water coverage ratio for the cases with the rough GDL surfaces is lower than that with the smooth GDL surface.The higher the roughness is

the less the GDL surface is covered by water.The pressure drop in the GCs increases with the increase of GDL surface roughness.