TRPIV experimental investigation of drag-reductionmechanism in turbulent boundary layerover superhydrophobic surfaces
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摘要: 利用高时间分辨率粒子图像测速(TRPIV)技术,开展超疏水壁面材料湍流边界层减阻机理的实验研究.在循环水槽中,对超疏水壁面和亲水壁面湍流边界层瞬时速度矢量场的时间序列进行了实验测量.得到了同一来流速度(0.17m/s)下超疏水壁面和亲水壁面湍流边界层的平均速度、湍流度及雷诺切应力沿法向的分布规律.提出了空间多尺度局部平均涡量的概念,并以此为特征量检测壁湍流发卡涡展向涡头的中心位置.用条件采样及空间相位平均技术提取了不同法向位置发卡涡展向涡头周围流向脉动速度和流线的空间拓扑,对发卡涡展向涡头的俯仰角进行了对比,并从鞍点-焦点动力系统的角度分析了发卡涡展向涡头附近的流线拓扑特征.研究表明:雷诺数约为13500时,相比亲水壁面,超疏水壁面实现了10.1%的减阻.超疏水壁面平均速度明显增大,雷诺切应力减小,流向湍流度减弱,发卡涡展向涡头俯仰角较小,近壁区相干结构的发展受到抑制.
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关键词:
- 湍流减阻 /
- 超疏水壁面 /
- 湍流边界层 /
- 高时间分辨率粒子图像测速(TRPIV) /
- 鞍点-焦点动力系统 /
- 空间多尺度局部平均涡量
Abstract: Drag-reduction in turbulent boundary layer (TBL) over superhydrophobic surfaces was investigated by the time-resolved particle image velocimetry (TRPIV). Time series of velocity vector fields in TBL over superhydrophobic surfaces and hydrophilic surfaces were measured in a cyclical water channel. The distributions of mean velocity profile, Reynolds shear stress and turbulence intensity along wall-normal direction were acquired at the same free-stream velocity (0.17m/s). The center of the head of hairpin vortex in wall turbulence was detected with the multi-scale spatial locally-averaged vorticity. Conditional sampling and phase average methods were utilized to extract the spatial topologies of spanwise vortices at different normal positions. Streamwise fluctuation velocity and the pitching angle of spanwise vortex in both cases were compared. The features of streamline topologies around spanwise vortex were analyzed from the saddle-focus dynamical system. Results revealed that a drag reduction of 10.1% is acquired if Reynolds numbers are about 13500. For superhydrophobic surfaces, the average velocity seems to be increased, Reynolds shear stress is decreased, streamwise turbulence intensity is weakened, the pitching angle of spanwise vortex is smaller, and the development of coherent structure near wall region is suppressed. -
[1] Barthlott W,Neinhuis C.Purity of the sacred lotus or escape from contamination in biological surfaces[J].Planta,1997,202(1):1-8. [2] Jiang C G,Xin S C,Wu C W.Drag reduction of a miniature boat with superhydrophobic grille bottom[J].AIP Advances,2011,1(3):032148.1-032148.8. [3] 常跃峰,姜楠.沟槽壁湍流多尺度相干结构实验研究[J].航空动力学报,2008,23(5):788-795. CHANG Yuefeng,JIANG Nan.Experimental study on coherent structure passive control and drag reduction in turbulent boundary layer with grooved surface[J].Journal of Aerospace Power,2008,23(5):788-795.(in Chinese) [4] 胡海豹,宋保维,刘占一,等.基于湍流边界层时均速度分布的脊状表面减阻规律研究[J].航空动力学报,2009,24(5):1040-1047. HU Haibao,SONG Baowei,LIU Zhanyi,et al.Research about the characteristic of drag reduction over riblets surface based on average velocity profile in the turbulent boundary layer[J].Journal of Aerospace Power,2009,24(5):1040-1047.(in Chinese) [5] 卢思,姚朝晖,郝鹏飞,等.具有微纳结构超疏水表面的槽道减阻特性研究[J].中国科学:物理学,力学,天文学,2010,40(7):916-924. LU Si,YAO Zhaohui,HAO Pengfei,et al.Investigation of drag reduction over superhydrophobic surfaces with micro-nano structures in a channel[J]. Scientia Sinica:Physica,Mechanica and Astronomica,2010,40(7):916-924.(in Chinese) [6] Gogte S,Vorobieff P,Truesdell R,et al.Effective slip on textured superhydrophobic surfaces[J].Physics of Fluids,2005,17(5):1441-1457. [7] Daniello R J,Waterhouse N E,Rothstein J P.Drag reduction in turbulent flows over superhydrophobic surfaces[J].Physics of Fluids,2009,21(8):085103.1-085103.9. [8] Henoch C,Krupenkin T,Kolodner P,et al.Turbulent drag reduction using superhydrophobic surfaces[R].AIAA-2006-3192,2006. [9] Min T,Kim J.Effects of hydrophobic surface on skin-friction drag[J].Physics of Fluids,2004,16(7):L55-L58. [10] Fukagata K,Kasagi N,Koumoutsakos P.A theoretical prediction of friction drag reduction in turbulent flow by superhydrophobic surfaces[J].Physics of Fluids,2006,18(5):051703.1-051703.4. [11] Bharat B,Yong C J,Kerstin K.Micro-,nano-and hierarchical structures for superhydrophobicity,self-cleaning and low adhesion[J].Philosophical Transactions of the Royal Society A:Mathematical,Physical and Engineering Sciences,2009,367(1894):1631-1672. [12] Cassie A B D,Baxter S.Wettability of porous surfaces[J].Transactions of the Faraday Society,1944,40:546-551. [13] Wenzel R N.Resistance of solid surfaces to wetting by water[J].Industrial & Engineering Chemistry,1936,28(8):988-994. [14] 郝鹏飞,汪幸愉,姚朝晖,等.疏水微槽道内层流减阻的实验研究[J].实验流体力学,2009,23(3):7-11. HAO Pengfei,WANG Xingyu,YAO Chaohui,et al.Experimental study on laminar drag reduction in micro-channels with superhydrophobic surfaces[J].Journal of Experiments in Fluid Mechanics,2009,23(3):7-11.(in Chinese) [15] 姜楠,管新蕾,于培宁.雷诺应力各向异性涡黏模型的层析TRPIV测量[J].力学学报,2012,44(2):213-221. JIANG Nan,GUAN Xinlei,YU Peining.Tomo-graphic TRPIV measurement of anisotropic eddy-viscosity model for coherent structure Reynolds stress[J].Chinese Journal of Theoretical and Applied Mechanics,2012,44(2):213-221.(in Chinese) [16] 姜楠,于培宁,管新蕾.湍流边界层相干结构空间拓扑形态的层析TRPIV测量[J].航空动力学报,2012,27(5):1113-1121. JIANG Nan,YU Peining,GUAN Xinlei.Tomo-TRPIV measurement of coherent structure spatial topology in turbulent boundary layer[J].Journal of Aerospace Power,2012,27(5):1113-1121.(in Chinese) [17] Adrian R J,Meinhart C D,Tomkins C D.Vortex organization in the outer region of the turbulent boundary layer[J].Journal of Fluid Mechanics,2000,422(1):1-54. [18] Elsinga G E,Marusic I.Evolution and lifetimes of flow topology in a turbulent boundary layer[J].Physics of Fluids,2010,22(1):015102.1-015102.8.
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