-
Superhydrophobic surfaces with micro- and nano-scale structures are conducible to maintaining a gas layer where prominent slippage effect exists. It has been demonstrated that the drag reduction of superhydrophobic surface increases with growing the fraction of the gas-water interface and the rising of the thickness of gas layer. Whereas a large thick gas layer on the superhydrophobic surface collapses easily under tangential water flow. Here, we present a new method to maintain large-scale gas layer by creating hydrophilic patterns at the superhydrophobic surface, on which the binding force of air on the solid surface can be caused by wettability difference. Through testing the states of gas layer trapped on surfaces with wettability differences equal to 54.8, 84.7, 103.6 and 144.0 in apparent contact angle, respectively, the conditions of maintaining gas layer are mainly considered. We demonstrate that the critical velocity, over which the gas layer begins to collapse under the tangential water flow, is positively correlated with the thickness of the gas layer and the wettability difference between the superhydrophobic area and hydrophilic area, however, this is negatively correlated with the width of the gas layer in the crosswise direction. It is noteworthy that even a centimeter-scale gas layer can be kept steady in ～0.9 m/s through this method. Furthermore, an obvious slip velocity up to ～25% of bulk velocity is observed at the gas-water interface, through measuring the velocity profile above the 0.6 cm-long, 0.5 cm-wide and 0.15 cm-thick gas layer by using the PIV technology. We anticipate that this novel method of gas entrapment under water will effectively widen the applications of superhydrophobic surfaces for drag reduction.
-
Keywords:
- superhydrophobic surface /
- hydrophilic surface /
- gas layer /
- slip
[1] Bechert D W, Bruse M, Hage W, Meyer R 2000 Naturwissenschaften 87 157
[2] Song D, Daniello R J, Rothstein J P 2014 Exp. Fluids 55 8
[3] Song D, Song B W, Hu H B, Du X S, Zhou F 2015 Phys. Chem. Chem. Phys. 17 21
[4] Hu H B, Du P, Huang S H, Wang Y 2013 Chin. Phys. B 22 074703
[5] Song B W, Guo Y H, Luo Z Z, Xu X H, Wang Y 2013 Acta Phys. Sin. 62 154701 (in Chinese) [宋保维, 郭云鹤, 罗莊竹, 徐向辉, 王鹰 2013 62 154701]
[6] Tretheway D C, Meinhart C D 2002 Phys. Fluids 14 9
[7] Ou J, Rothstein J P 2005 Phys. Fluids 17 10
[8] Busse A, Sandham N D, McHale G, Newton M I 2013 J. Fluid Mech. 727 488
[9] Kwon B H, Kim H H, Jeon H J, Kim M C, Lee I, Chun S, Go J S 2014 Exp. Fluids 55 1722
[10] Samaha M A, Tafreshi H V, Gad-el-Hak M 2011 Phys. Fluids 23 012001
[11] Jagdish B N, Brandon T Z X, Kwee T J, Dev A K 2014 J. Ship Res. 58 30
[12] Song B W, Ren F, Hu H B, Guo Y H 2014 Acta Phys. Sin. 63 054708 (in Chinese) [宋保维, 任峰, 胡海豹, 郭云鹤 2014 63 054708]
[13] Wang B, Wang J D, Chen D R 2014 Acta Phys. Sin. 63 074702 (in Chinese) [王宝, 汪家道, 陈大融 2014 63 074702]
[14] McHale G 2007 Langmuir 23 15
[15] Furmidge C G L 1962 J. Colloid Sci. 17 309
-
[1] Bechert D W, Bruse M, Hage W, Meyer R 2000 Naturwissenschaften 87 157
[2] Song D, Daniello R J, Rothstein J P 2014 Exp. Fluids 55 8
[3] Song D, Song B W, Hu H B, Du X S, Zhou F 2015 Phys. Chem. Chem. Phys. 17 21
[4] Hu H B, Du P, Huang S H, Wang Y 2013 Chin. Phys. B 22 074703
[5] Song B W, Guo Y H, Luo Z Z, Xu X H, Wang Y 2013 Acta Phys. Sin. 62 154701 (in Chinese) [宋保维, 郭云鹤, 罗莊竹, 徐向辉, 王鹰 2013 62 154701]
[6] Tretheway D C, Meinhart C D 2002 Phys. Fluids 14 9
[7] Ou J, Rothstein J P 2005 Phys. Fluids 17 10
[8] Busse A, Sandham N D, McHale G, Newton M I 2013 J. Fluid Mech. 727 488
[9] Kwon B H, Kim H H, Jeon H J, Kim M C, Lee I, Chun S, Go J S 2014 Exp. Fluids 55 1722
[10] Samaha M A, Tafreshi H V, Gad-el-Hak M 2011 Phys. Fluids 23 012001
[11] Jagdish B N, Brandon T Z X, Kwee T J, Dev A K 2014 J. Ship Res. 58 30
[12] Song B W, Ren F, Hu H B, Guo Y H 2014 Acta Phys. Sin. 63 054708 (in Chinese) [宋保维, 任峰, 胡海豹, 郭云鹤 2014 63 054708]
[13] Wang B, Wang J D, Chen D R 2014 Acta Phys. Sin. 63 074702 (in Chinese) [王宝, 汪家道, 陈大融 2014 63 074702]
[14] McHale G 2007 Langmuir 23 15
[15] Furmidge C G L 1962 J. Colloid Sci. 17 309
Catalog
Metrics
- Abstract views: 6651
- PDF Downloads: 273
- Cited By: 0
下载:
