超疏水壁面湍流边界层减阻机理的TRPIV实验

发布时间：2018-10-20 08:15

【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13 500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.
[Abstract]:An experimental study on drag reduction mechanism of turbulent boundary layer of superhydrophobic wall material was carried out using high time resolution particle image velocimetry (TRPIV) technique. The time series of the instantaneous velocity vector field in the turbulent boundary layer of superhydrophobic wall and hydrophilic wall are measured experimentally in a circulating water tank. The distributions of mean velocity, turbulence degree and Reynolds shear stress in the turbulent boundary layer of superhydrophobic wall and hydrophilic wall under the same inflow velocity (0.17m/s) are obtained. The concept of spatial multi-scale local average vorticity is proposed, which is used as the characteristic quantity to detect the center position of the spanned vortex head of wall turbulence hairpin vortex. By using conditional sampling and spatial phase averaging techniques, the flow direction pulsation velocities and streamline spatial topologies around the spanned vortex head in different normal positions were extracted, and the pitch angle of the hairpin vortex spanned vortex head was compared. From the point of view of the saddle point-focus dynamic system, the topological characteristics of streamlines near the spanned vortex head of the hairpin are analyzed. The results show that when Reynolds number is about 13 500, the drag reduction of superhydrophobic wall is 10.1% compared with hydrophilic wall. The average velocity of the superhydrophobic wall increases obviously, the Reynolds shear stress decreases, the turbulence in the flow direction weakens, the pitching angle of the hairpin vortex spanned vortex head is small, and the development of coherent structures near the wall is restrained.
【作者单位】：天津大学机械工程学院力学系;清华大学航天航空学院工程力学系;天津大学天津市现代工程力学重点实验室;
【基金】：国家自然科学基金(11272233,11332006,11411130150) 国家重点基础研究发展计划(2012CB720101,2012CB720103)
【分类号】：O357.5

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