Optimal fluxes and Reynolds stresses
Optimal fluxes and Reynolds stresses
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最佳通量和雷诺应力
DOI：
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发表时间：
2016
影响因子：
3.7
通讯作者：
J. Jiménez
中科院分区：
文献类型：
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作者：
J. Jiménez
注意到守恒律中的通量，例如湍流剪切流动量方程中的雷诺应力，或各向异性湍流中的谱能通量，仅定义为任意螺线管场。虽然这通常对长时间平均值并不重要，但当在大涡模拟中对通量进行局部建模时，或在对流和叶栅分析中，这一点变得很重要。作为一个例子，介绍了一种数值方法来计算标量守恒方程中的通量，使得它们的总积分量最小。其结果是一个无旋矢量场，来自一个潜在的，从而最大限度地减少无菌通量'电路'。该算法被推广到张量通量，并应用于湍流通道中的动量转移。所得的瞬时雷诺应力与传统的表达式进行了比较，发现有很大的不同。这表明，一些简单的子网格模型的所谓的缺点可能是代表性的文物，这可能是同样的湍流应力的不稳定性的属性。
It is remarked that fluxes in conservation laws, such as the Reynolds stresses in the momentum equation of turbulent shear flows, or the spectral energy flux in anisotropic turbulence, are only defined up to an arbitrary solenoidal field. While this is not usually significant for long-time averages, it becomes important when fluxes are modelled locally in large-eddy simulations, or in the analysis of intermittency and cascades. As an example, a numerical procedure is introduced to compute fluxes in scalar conservation equations in such a way that their total integrated magnitude is minimised. The result is an irrotational vector field that derives from a potential, thus minimising sterile flux ‘circuits’. The algorithm is generalised to tensor fluxes and applied to the transfer of momentum in a turbulent channel. The resulting instantaneous Reynolds stresses are compared with their traditional expressions, and found to be substantially different. This suggests that some of the alleged shortcomings of simple subgrid models may be representational artefacts, and that the same may be true of the intermittency properties of the turbulent stresses.