Turbulent Drag Reduction Using Superhydrophobic Surfaces

Superhydrophobic surfaces are known to exhibit reduced viscous drag due to "slip" associated with a layer of air trapped at the liquid-solid interface. It is expected that this slip will lead to reduced turbulent skin-friction drag in external flows at higher Reynolds numbers in both the laminar and turbulent regimes. Results are presented from experiments exploring this effect. Large-area Superhydrophobic test surfaces have been fabricated and tested in a water tunnel, measuring drag in both the laminar and transitional regimes at velocities up to 1.4 m/s. Drag reduction of approximately 50 % is observed for laminar flow. Lower levels of drag reduction are observed at higher speeds after the flow has transitioned to turbulence. I