平板湍流边界层瞬时摩擦阻力的光学测量和统计分析  

Optical Measurement and Statistical Analysis of Instantaneous Wall-Shear Stress in a Turbulent Boundary Layer

作　　者：申俊琦[1] 王建杰 潘翀[1,2] SHEN Jun-qi;WANG Jian-jie;PAN Chong(Key Laboratory of Fluid Mechanics of Ministry of Education,Beihang University,Beijing 100191,China;Aircraft and Propulsion Laboratory,Ningbo Institute of Technology,Beihang University,Ningbo 315100,China)

机构地区：[1]北京航空航天大学流体力学教育部重点实验室,北京100191 [2]北京航空航天大学宁波创新研究院先进飞行器与空天动力创新研究中心,浙江宁波315100

出　　处：《气体物理》2020年第5期13-23,共11页Physics of Gases

基　　金：国家自然科学基金(11490552,91852206,11721202)。

摘　　要：采用近壁粒子图像测速(particle image velocimetry,PIV)技术实现了中低Reynolds数光滑平板湍流边界层瞬时摩擦阻力的测量.发展了单行互相关算法和迭代拟合技术估算瞬时摩擦阻力,其法向空间分辨率可达到2~4 pixel.作为对比,同时分析了相似Reynolds数范围的直接数值模拟数据.统计结果表明:摩擦阻力的脉动强度随Reynolds数升高呈现对数增长趋势,证实了外区大/超大尺度结构对壁面的影响.谱分析结果表明近壁区的低速条带结构主导着摩擦阻力的多尺度脉动特性,外区大/超大尺度结构对摩擦阻力的印迹作用较小,其主要通过调制作用实现对摩擦阻力的影响,这一结论可以从瞬时摩擦阻力的偏度以及概率密度函数曲线具有Reynolds数不变性得到进一步证实.The near-wall PIV technique was utilized to measure the instantaneous wall-shear stress(WSS)in a smooth-wall turbulent boundary layer at low-to-moderate Reynolds numbers.The algorithm of single-row cross correlation,together with a newly proposed iterative fitting method,was used to estimate the WSS.The spatial resolution of WSS was about 2~4 pixel in the wall-normal direction.Existing direct numerical simulation datasets in the same Reτrange were also analyzed for direct comparison.The fluctuating intensity of WSS was found to follow the empirical log-law correlation with Reτ,indicating the existence of the influence of outer-layer large-scale or very-large-scale motions(LSMs/VLSMs)on the wall.A further spectra analysis indicates that the near wall low-speed streaks dominate the dynamic behavior of the WSS.Combined with weak Re-dependency of both the skewness and probability density function of fluctuating WSS,it can be inferred that the LSMs/VLSMs leave a mild footprint on the wall.Instead,the amplitude modulation effect is inferred to play a more prominent role in affecting the statistics and multi-scale characteristics of WSS.

关 键 词：近壁PIV技术 湍流边界层 瞬时摩擦阻力 统计分析 多尺度脉动特性 调制作用 

分 类 号：O357.5[理学—流体力学]