Drag reduction characteristics and flow field analysis of textured surface

A textured surface with a micro-groove structure exerts a distinct characteristic on drag reduction behavior. The fluid dynamic models of four textured surfaces are constructed in various profile geometries. Computational fluid dynamics is used to study the friction factors and drag reduction properties with various flow speeds on the textured surfaces. The friction coefficient varieties in the interface between the fluid and the textured surface are examined according to the simulation of the four geometries with V-shaped, saw tooth, rectangular, and semi-circular sections. The drag reduction efficiencies decrease with the increase in water velocity while it is less than a certain value. Moreover, the simulation results of the velocity, shear stress, energy, and turbulence effect on the V-shaped groove surface are presented in comparison with those of the smooth surface to illustrate the drag reduction mechanism. The results indicate that the peaks of the V-shaped grooves inhibit the lateral movement of the turbulent flow and generate the secondary vortex, which plays a key role in the impeding momentum exchange, thereby decreasing turbulent bursting intensity and reducing shear stress in the near-wall flow field. The kinetic energy and turbulence analysis shows that the vortex in the near-wall flow field on the textured surface is more stable compared to that on the smooth surface.