Correlation between small-scale velocity and scalar fluctuations in a turbulent channel flow
Correlation between small-scale velocity and scalar fluctuations in a turbulent channel flow
复制标题
DOI：
10.1017/s0022112008005569
复制
发表时间：
2009-05-25
影响因子：
3.7
通讯作者：
Kawamura, Hiroshi
中科院分区：
文献类型：
--
作者：
Abe, Hiroyuki;Antonia, Robert Anthony;Kawamura, Hiroshi
采用直接数值模拟方法研究了具有被动标量输运的槽道湍流小尺度速度场与标量场之间的关系。基于摩擦速度和通道半宽的雷诺数等于180、395和640，分子普朗特数为0.71。重点是涡度矢量的分量和标量导数矢量的分量之间的相互关系。在壁面附近，由于动量条纹和热条纹之间几乎完全对应，两个矢量的不同分量之间具有密切的相似性。随着距离壁的距离的增加，相关性的大小变得更小，但仍然是不可忽略的无处不在的通道中，由于内部区域中的内部剪切和标量层的存在和外部区域中的大尺度运动的背面。的标量耗散率，这是很重要的小尺度标量混合的拓扑结构，示出与有组织的结构。标量耗散率的最优方向是壁面附近的平均应变率方向和外部区域的波动压缩应变率方向。后一区域与几种湍流有许多共同的特征，即主导结构是片状的，与能量耗散率的相关性比涡度拟能好。
Direct numerical simulations of a turbulent channel flow with passive scalar transport are used to examine the relationship between small-scale velocity and scalar fields. The Reynolds number based on the friction velocity and the channel half-width is equal to 180, 395 and 640, and the molecular Prandtl number is 0.71. The focus is on the interrelationship between the components of the vorticity vector and those of the scalar derivative vector. Near the wall, there is close similarity between different components of the two vectors due to the almost perfect correspondence between the momentum and thermal streaks. With increasing distance from the wall, the magnitudes of the correlations become smaller but remain non-negligible everywhere in the channel owing to the presence of internal shear and scalar layers in the inner region and the backs of the large-scale motions in the outer region. The topology of the scalar dissipation rate, which is important for small-scale scalar mixing, is shown to be associated with the organized structures. The most preferential orientation of the scalar dissipation rate is the direction of the mean strain rate near the wall and that of the fluctuating compressive strain rate in the outer region. The latter region has many characteristics in common with several turbulent flows; viz. the dominant structures are sheetlike in form and better correlated with the energy dissipation rate than the enstrophy.