Large-eddy simulation of homogeneous turbulence and diffusion in stably stratified shear flow
Large-eddy simulation of homogeneous turbulence and diffusion in stably stratified shear flow
复制标题
稳定分层剪切流中均匀湍流和扩散的大涡模拟
DOI：
10.1017/s0022112094002831
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发表时间：
1994
影响因子：
3.7
通讯作者：
U. Schumann
中科院分区：
文献类型：
--
作者：
H. Kaltenbach;T. Gerz;U. Schumann
利用大涡模拟方法，对梯度理查森数为0 ~ 1的中性稳定剪切层流进行了均匀湍流模拟。我们调查的三个被动的物种，在垂直，下游或横流方向上具有均匀梯度的湍流输送。与以前的测量结果进行了比较，在实验室和稳定的大气边界层，以及直接数值模拟的结果。计算的和测量的流动特性一般在测量的分散范围内彼此一致。在强分层时，弗劳德数成为相关的流动控制参数。稳定层结抑制垂直翻转和混合时，弗劳德数的反转翻转时标的基础上超过约3的临界值。湍流扩散系数张量是强各向异性和非对称的。然而，在剪切流中，只有垂直和横流的对角分量才有实际意义。在强层结时，垂直扩散系数远小于横流扩散系数。这种各向异性比二阶闭合模型预测的要强。下游和横流方向的湍流通量遵循经典的混合长度模型。
By means of large-eddy simulation, homogeneous turbulence is simulated for neutrally and stably stratified shear flow at gradient-Richardson numbers between zero and one. We investigate the turbulent transport of three passive species which have uniform gradients in either the vertical, downstream or cross-stream direction. The results are compared with previous measurements in the laboratory and in the stable atmospheric boundary layer, as well as with results from direct numerical simulations. The computed and measured flow properties agree with each other generally within the scatter of the measurements. At strong stratification, the Froude number becomes the relevant flow-controlling parameter. Stable stratification suppresses vertical overturning and mixing when the inverse Froude number based on a turn-over timescale exceeds a critical value of about 3. The turbulent diffusivity tensor is strongly anisotropic and asymmetric. However, only the vertical and the cross-stream diagonal components are of practical importance in shear flows. The vertical diffusion coefficient is much smaller than the cross-stream one at strong stratification. This anisotropy is stronger than predicted by second-order closure models. Turbulence fluxes in downstream and cross-stream directions follow classical mixing-length models.