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It is well known that surface structures play an important role on superhydrophobicity.Pervious researches show that the hydrophobicity is determined by not only the wettability of the channel but also the surface topography.In the present work,a lattice Boltzmann model was developed to investigate the effects of surface structures on both wettabilities and flow dynamics in a microchannel.The theory of wetting transition was discussed.Three types including triangular,rectangle and hierarchical shaped structures were constructed on the surface to examine the effects on wettabilities and drag reduction effects.It was found that flow behaviours were strongly affected by the wettability and topography of the channel.In particular,different sizes of roughness were investigated on drag reduction effects.The simulation results indicated that hierarchical structures can improve the hydrophobicity significantly while rectangular roughness can only improve the hydrophobicity when the ratio of height and distance h/d of the roughness is below a critical value.