The structure of fine-scale scalar mixing in gas-phase planar turbulent jets
The structure of fine-scale scalar mixing in gas-phase planar turbulent jets
复制标题
气相平面湍流射流中细尺度标量混合的结构
DOI：
10.1017/s002211200300466x
复制
发表时间：
2003
影响因子：
3.7
通讯作者：
N. Clemens
中科院分区：
文献类型：
--
作者：
L. Su;N. Clemens
通过测量平面气相湍流射流中的三分量标量梯度场和标量能量耗散率场，研究了平面气相湍流射流中的细尺度标量混合。同时平面瑞利散射和平面激光诱导荧光，应用在平行的平面，产生三维标量场测量。空间分辨率足以允许在所有三个空间方向上进行区分。数据范围的外尺度雷诺数从3290到8330。直接测量标量耗散结构（层）的厚度表明，厚度与外尺度雷诺数的比例为$\hbox{\it Re}_\delta^{-3/4}$，符合Kolmogorov/Batchelor标度。平均层厚度由关系式$\lambda_D= 14.5\，\delta\，\hbox{\it Re}_\delta^{-3/4}\hbox{\it Sc}^{-1/2}$描述。这里没有证据表明泰勒标度（$\lambda_D\propto\delta\，\hbox{\it Re}_\delta^{-1/2}$）在标量耗散过程中起着重要作用。目前的数据解决了一系列的长度尺度从耗散尺度到近射流全宽，因此可以用于在大涡模拟（LES）的标量混合的亚网格模型的先验测试。比较两个模型的亚网格标量方差，尺度相似性模型和基于梯度的模型，表明尺度相似性模型是更准确的大LES过滤器的大小。
Fine-scale scalar mixing in gas-phase planar turbulent jets is studied using measurements of three-component scalar gradient and scalar energy dissipation rate fields. Simultaneous planar Rayleigh scattering and planar laser-induced fluorescence, applied in parallel planes, yield the three-dimensional scalar field measurements. The spatial resolution is sufficient to permit differentiation in all three spatial directions. The data span a range of outer-scale Reynolds numbers from 3290 to 8330. Direct measurement of the thicknesses of scalar dissipation structures (layers) shows that the thicknesses scale with outer-scale Reynolds number as $\hbox{\it Re}_\delta^{-3/4}$, consistent with Kolmogorov/Batchelor scaling. Average layer thicknesses are described by the relation $\lambda_D=14.5\,\delta\, \hbox{\it Re}_\delta^{-3/4}\hbox{\it Sc}^{-1/2}$. There is no evidence here that Taylor scaling ($\lambda_D\propto\delta\, \hbox{\it Re}_\delta^{-1/2}$) plays a significant role in the scalar dissipation process. The present data resolve a range of length scales from the dissipation scales up to nearly the jet full width, and thus can be used in a priori testing of subgrid models for scalar mixing in large-eddy simulations (LES). Comparison of two models for subgrid scalar variance, a scale-similarity model and a gradient-based model, indicates that the scale-similarity model is more accurate at larger LES filter sizes.