RT Journal Article SR Electronic T1 Significant and stable drag reduction with air rings confined by alternated superhydrophobic and hydrophilic strips JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP e1603288 DO 10.1126/sciadv.1603288 VO 3 IS 9 A1 Hu, Haibao A1 Wen, Jun A1 Bao, Luyao A1 Jia, Laibing A1 Song, Dong A1 Song, Baowei A1 Pan, Guang A1 Scaraggi, Michele A1 Dini, Daniele A1 Xue, Qunji A1 Zhou, Feng YR 2017 UL http://advances.sciencemag.org/content/3/9/e1603288.abstract AB Superhydrophobic surfaces have the potential to reduce the viscous drag of liquids by significantly decreasing friction at a solid-liquid interface due to the formation of air layers between solid walls and interacting liquids. However, the trapped air usually becomes unstable due to the finite nature of the domain over which it forms. We demonstrate for the first time that a large surface energy barrier can be formed to strongly pin the three-phase contact line of air/water/solid by covering the inner rotor of a Taylor-Couette flow apparatus with alternating superhydrophobic and hydrophilic circumferential strips. This prevents the disruption of the air layer, which forms stable and continuous air rings. The drag reduction measured at the inner rotor could be as much as 77.2%. Moreover, the air layers not only significantly reduce the strength of Taylor vortexes but also influence the number and position of the Taylor vortex pairs. This has strong implications in terms of energy efficiency maximization for marine applications and reduction of drag losses in, for example, fluid transport in pipelines and carriers.