Abstract: A droplet with constant driving force moving inside a micro-channel is studied in a lattice Boltzmann model and a Shan-Chen multiphase model.Flow regimes under different wall wettability and topography are investigated.It is clarified that hydrophobic surface with certain roughness can reduce fluid flow resistance.It is found that flow behaviors are strongly affected by wall wettability and surface roughness.It shows that the method is efficient and accurate.It has good prospect on the study of drag reduction of microscopic seepage of reservoirs.

Key words: drag reduction, wettability, nanoparticle, multiphase-flow, Lattice Boltzmann model