An experimental investigation of groove control for reducing drag in a flat turbulent boundary layer

The paper proposes two techniques for processing microstructure grooves and examines the factors affecting groove formation rate. A novel roller shaft hot stamping equipment has been developed to efficiently produce straight groove film at a high forming rate. Furthermore, precise preparation of curved grooves is achieved through fine milling technology. To determine the optimal process parameter combination for maximum groove forming rate, an orthogonal experimental design approach is utilized for preparing both submicron-level grooves. The characteristics of the developed turbulent boundary layer via groove control are measured by means of the Hot Wire Anemometer (HWA) on the built flat-plate wind tunnel experimental platform. The experimental data show that the average velocity profile undergoes a progressive increase when subjected to groove control, leading to a decrease in friction drag. Also, it results in a decrease in the magnitude of turbulent fluctuations. The curved groove exhibits a localized decrease in drag by as much as 10.3%, while the straight groove achieves a drag reduction rate of up to 8%. As the dimensionless amplitude of the curved groove surpasses 60, the drag reduction effect diminishes and exhibits less efficacy in comparison to the straight groove. This paper experimentally investigates groove control to reduce drag in a flat turbulent boundary layer at Reτ≈2300. Two microstructure groove processing techniques are proposed and their efficiency studied via orthogonal experimental design. Both straight and curved grooves are shown feasible with high formation efficiency. Using a flat-plate wind tunnel and Hot Wire Anemometer (HWA), the study determines that grooves lead to increased average velocity profiles, reducing friction drag and turbulent fluctuations. Adjusting groove parameters proves effective in reducing turbulent friction drag.