Drag reduction performance of grooved superhydrophobic surfaces

In the field of engineering applications, reducing frictional drag in turbulent flows is imperative to enhance energy efficiency. This study investigates the potential of grooved superhydrophobic surfaces (GSHS) in reducing drag in turbulent flows under ventilation conditions. A systematic investigation is conducted to examine the effects of effective gas film thickness (thg) and groove width (Wg) on drag reduction rate (DR) and gas film state at various Reynolds numbers (Re). The drag characteristics and reduction effects of smooth surfaces (SS), grooved surfaces (GS), superhydrophobic smooth surfaces (SHS), and GSHS are also compared. The experimental results indicate that SS and GS surfaces do not show any notable drag reduction under ventilation and may even result in a drag increase. In contrast, SHS and GSHS exhibit considerable drag reduction effects under ventilation, with the DR of GSHS increasing significantly with thg. The drag reduction effect is influenced by the interplay between thg and Wg. At varying Re, GSHS has been demonstrated to achieve substantial DR ranging from 44% to 46%. This study provides new insights into drag reduction in underwater turbulence and offers theoretical support for drag reduction techniques in engineering applications, such as underwater vehicles and pipeline flows.