Inner and outer layer turbulence over a superhydrophobic surface with low roughness level at low Reynolds number
Inner and outer layer turbulence over a superhydrophobic surface with low roughness level at low Reynolds number
复制标题
DOI：
10.1063/1.5004398
复制
发表时间：
2017-09
影响因子：
4.6
通讯作者：
W. Rowin;J. Hou;S. Ghaemi
中科院分区：
文献类型：
--
作者：
W. Rowin;J. Hou;S. Ghaemi
采用远程微观粒子跟踪测速技术（micro-PTV）和粒子图像测速技术，分别对超疏水表面（SHS）上湍流通道的内层和外层进行了表征。通道流动在低雷诺数ReH = 4400（基于全通道高度和0.174 m/s体速度）下运行，相当于Reτ = 140（基于半通道高度和摩擦速度）。SHS采用喷涂方式产生，经壁单元归一化的壁面粗糙度均方根为k+rms = 0.11。微ptv显示在SHS上的滑移速度为0.023 m/s（约为体速度的13%），对应于滑移长度为~ 200 μm。基于线性粘性亚层斜率的阻力减小~ 19%，基于Rastegari和Akhavan的解析表达式的阻力减小22% [J]。流体力学[j] .武汉理工大学学报（自然科学版）。基于相应的摩擦速度，在SHS上的还原Reτ为~ 125，这是湍流re的下限。
The inner and outer layers of a turbulent channel flow over a superhydrophobic surface (SHS) are characterized using simultaneous long-range microscopic particle tracking velocimetry (micro-PTV) and particle image velocimetry, respectively. The channel flow is operated at a low Reynolds number of ReH = 4400 (based on full channel height and 0.174 m/s bulk velocity), equivalent to Reτ = 140 (based on half channel height and friction velocity). The SHS is produced by spray coating, and the root-mean-square of wall roughness normalized by wall-unit is k+rms = 0.11. The micro-PTV shows 0.023 m/s slip velocity over the SHS (about 13% of the bulk velocity), which corresponds to a slip-length of ∼200 μm. A drag reduction of ∼19% based on the slope of the linear viscous sublayer and 22% based on an analytical expression of Rastegari and Akhavan [J. Fluid Mech. 773, R4 (2015)] realized. The reduced Reτ over the SHS based on the corresponding friction velocity is ∼125, which is in the lower limit of a turbulence re...