Effect of vortex frictional drag reduction on ordered microstructures

Abstract

The speed and energy consumption are important indices to evaluate the performance of surface and underwater vehicles. The frictional drag is a key factor influencing the speed and energy consumption of vehicles. We studied the flow field and the drag reduction for different transverse microstructures and found that vortices could be formed in the transverse structures, which reduced the frictional drag. We fabricated different apertures of nanoporous TiO2 films on smooth Ti foils by a two-step low-cost anodic oxidation process. Compared with smooth foils, the nanoporous with a depth of 100 nm and diameter 5.1 μm can decrease drag by 40% under the 1.5 m s−1 velocity condition. The results showed that sliding friction changes to rolling friction at the solid-liquid interface in the transverse grooves. The technology has practical application in drag reduction.