壁湍流相干结构尺度及边界层内的SL标度律

利用高分辨率、高帧率PIV系统对湍流边界层中相干结构的多种空间尺度和边界层内SL 标度律在不同尺度下的具体表达形式进行了实验研究. 实验在两个动量损失厚度雷诺数 (Re_{\theta}=628.5和Re_{\theta}=1032.9)下测量平板湍流边界层中缓冲 层、对数区和外区的二维瞬时速度场. 应用 小波分析以及传统的统计学方法，在垂直于平板和平行于平板的平面内考察平板湍流边界层 中存在的相干结构的流向和展向尺度，并与已知的相干结构尺度实验结果进行了对比分析. 利用在动量损失厚度雷诺数628.5下测得的数据，对多种脉动结构(脉动速度结构等) 的空间关系及其标度律进行了研究. 第2项工作直接利用湍流边界层空间速度分布，对多种 流场尺度结构内部的She-Leveque(简称SL)标度律及自相似律进行了验证. 结果表明，各 单一流场尺度结构内部，流向脉动速度{\pmb u}'、法向脉动速度{\pmb v}'及 脉动涡分量\d {\pmb v}'/\d {\pmb x}的统计结构量均存在明显的标度律，标度 指数的形式与自相似律和SL标度律均非常吻合，只是常数随流场尺度的不同而不同， 且呈现一定的规律性. 但对于结构量的五阶矩随距离l的研究表明，自相似律和SL 标度律成立的范围并不完全一致，同时标度律成立的范围大小与流场尺度有明显关系.

EXPERIMENTAL STUDIES ON SL SCALING LAW AND SPATIAL SCALES OF COHERENT STRUCTURES IN NEAR-WALL TURBULENT BOUNDARY LAYER

In this paper, a PIV system is used to measure the scales of large scale coherent structures in the turbulent boundary layer of a flat plate. The streamwise and spanwise scales of coherent structures at Re_{\theta }=628.5 and 1032.9 are obtained by wavelet analysis and traditional statistic methods. Multi-scale spatial vector distributions of {\pmb u}', {\pmb v}' and \d {\pmb v}' / \d {\pmb x} obtained by wavelet analysis in the turbulent boundary layer at Re_{\theta }=628.5 are used to verify the SL scaling law and the self-similarity law. It is found that at a single scale of the flow field, the three statistical structures are matched well with the SL law and the self-similarity law, respectively, but the parameters of the SL law are not unique, but varying with flow scales. From the relation between S_{5}, and l (the distance), inertia ranges are found not the same for the SL scaling law and the self-similarity law, but varying also with the scale.