Experimental Investigation of Viscous Drag Reduction, Regarding Superhydrophobic Nano-Coating in Laminar and Turbulent Flows

In this research، effects of superhydrophobic nano-coating on frictional drag coefficient have been investigated. A rotating disc apparatus is 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 is prepared، using sol-gel method and is able to produce a contact angle of 160 degrees. Experiments were performed in the range of Reynolds number from 105 to 4×106. The results show about 30% drag reduction in laminar flows as well as about 15% drag reduction in turbulent flows.