In this paper, four types of micro-patterned surfaces, which are covered with ridge-shaped grooves, V-shaped grooves, shield-shaped grooves and straight slot grooves, are employed to investigate the drag reduction effect. Lattice Boltzmann method (LBM), a new numerical approach on mescoscopic level, is used to conduct the numerical simulations. The micro-grooved surfaces possess the drag reduction performance because the micro-structure affects the flow beahviours. The existence of the vortices formed within the grooves not only decrease the shear force between fluid and walls but also reduce the contact area between fluid and walls, which can lead to a reduction of pressure loss. The different grooved-surfaces have different degrees of drag reduction abilities: ridge-shaped grooves > V-shaped grooves > shield shaped grooves > straight slot grooves. Besides, the geometrical optimizations for the ridge-shaped grooves, which show the highest drag reduction performance, are performed as well. The results suggest that, for the purpose of drag reduction, the ridge-shaped grooves with smaller width-height ratio are recommended for the lower Reynolds number flow while the ridge-shape grooves with larger width-height ratio are more suitable for the larger Reynolds number flow.

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