壁湍流相干结构尺度及边界层内的SL标度律

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

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(Reθ=628．5和Reθ=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u’、法向脉动速度v’及脉动涡分量dv’／dx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．

In this paper, a PV 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 Reθ = 628.5 and 1032.9 are obtained by wavelet analysis and traditional statistic methods. Multi-scale spatial vector distributions of u′, v′ and dv′/dx obtained by wavelet analysis in the turbulent boundary layer at Reθ = 628.5 are used to verify the SL scaling law and the serf-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 serf-similarity law, respectively, but the parameters of the SL law are not unique, but varying with flow scales. From the relation between S5, and l （the distance）, inertia ranges are found not the same for the SL scaling law and the serf-similarity law, but varying also with the scale.