Experimental investigation of viscous drag reduction of superhydrophobic nano-coating in laminar and turbulent flows

In this research, effects of superhydrophobic nano-coating on frictional drag force have been investigated. The result of this study could be considered to be used as a method in applications concerned with fuel consumption reduction, less CO2 emission and environmental problems as well as speed increase; while, its significance can also be of great use in marine applications. A rotating disc apparatus was used as the experimental set-up to compare the frictional drag force on an aluminum disc with TiO2 superhydrophobic nano-coating and a smooth coatless aluminum disc. The superhydrophobic nano-coating was prepared using sol-gel method and was shown to be able to produce a contact angle of about 160°. Experiments were performed in the Reynolds numbers, ranging from 105 to 2 × 106. Results indicated the drag reduction values of up to 30% and 15% in laminar and turbulent flows, respectively.