High Freestream Turbulence Effects on Turbulent Boundary Layers
High Freestream Turbulence Effects on Turbulent Boundary Layers
复制标题
高自由流湍流对湍流边界层的影响
DOI：
10.1115/1.2817374
复制
发表时间：
1996
影响因子：
2
通讯作者：
D. Bogard
中科院分区：
文献类型：
--
作者：
K. Thole;D. Bogard
高的自由流湍流度显著改变了湍流边界层的特性。对于湍流度为7%或更低的自由流，已经进行了大量研究，但使用湍流度大于10%的研究基本上局限于对壁面剪应力和换热的影响。本文给出了湍流边界层与湍流度为10%~20%的自由流相互作用的边界层统计测量结果。本文报道的边界层统计数据包括平均速度和均方根速度、速度相关系数、长度尺度和功率谱。尽管如谱和长度尺度测量所示，当自由流湍流度较高时，自由流湍流涡能穿透边界层，但平均速度分布仍呈现对数线性区域。对总剪应力(湍流剪应力和粘性剪应力)的直接测量证实了对数定律在高自由流湍流水平下的有效性。边界层外部区域的速度缺陷明显减少，导致尾迹参数为负值。只有当自由流湍流度超过边界层产生均方根速度时，脉动均方根速度才会受到影响。长度尺度和功率谱测量表明，大尺度湍流涡穿透到壁面的y+=15范围内。
High freestream turbulence levels significantly alter the characteristics of turbulent boundary layers. Numerous studies have been conducted with freestreams having turbulence levels of 7 percent or less, but studies using turbulence levels greater than 10 percent have been essentially limited to the effects on wall shear stress and heat transfer. This paper presents measurements of the boundary layer statistics for the interaction between a turbulent boundary layer and a freestream with turbulence levels ranging from 10 to 20 percent. The boundary layer statistics reported in this paper include mean and rms velocities, velocity correlation coefficients, length scales, and power spectra. Although the freestream turbulent eddies penetrate into the boundary layer at high freestream turbulence levels, as shown through spectra and length scale measurements, the mean velocity profile still exhibits a log-linear region. Direct measurements of total shear stress (turbulent shear stress and viscous shear stress) confirm the validity of the log-law at high freestream turbulence levels. Velocity defects in the outer region of the boundary layer were significantly decreased resulting in negative wake parameters. Fluctuating rms velocities were only affected when the freestream turbulence levels exceeded the levels of the boundary layer generated rms velocities. Length scales and power spectra measurements showed large scale turbulent eddies penetrate to within y+ = 15 of the wall.