Three dimensional numerical simulation of gas-liquid two-phase flow patterns in a polymer-electrolyte membrane fuel cells gas flow channel

► VOF method was employed to investigate gas-liquid two-phase flow patterns in a large PEM fuel cell cathode side gas flow channel. ► Three stages of droplet behavior are identified: emergence and merging, accumulation on the side walls and detachment from the top wall. ► Flow pattern evolves from corner droplet flow to top wall film flow, annular flow, and finally slug flow when increasing liquid injection rates. ► Hydrophobic GDL surface is helpful to expel water from the GDL surface, but increases the pressure drop. Hydrophilic channel wall reduces the pressure drop, but increases the GDL water coverage ratio slightly and the water residence time.