Two phenomenological constants explain similarity laws in stably stratified turbulence.
Two phenomenological constants explain similarity laws in stably stratified turbulence.
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DOI：
10.1103/physreve.89.023007
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发表时间：
2013-12
期刊：
影响因子：
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通讯作者：
G. Katul;A. Porporato;Stimit Shah;E. Bou‐Zeid
中科院分区：
文献类型：
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作者：
G. Katul;A. Porporato;Stimit Shah;E. Bou‐Zeid
在稳定分层的湍流中，与热量的涡流扩散率或等效的湍流普朗特数 (Pr(t)) 相关的混合效率充满了复杂的动力学，这些动力学源于湍流的剪切生成与密度梯度消散之间的尺度相互作用。大量数据和数值模拟一致认为 Pr(t) 和理查森数 (R(i)) 之间存在近乎普遍的关系，该关系编码了浮力耗散对于湍流动能的机械产生的相对重要性。如果调用压力应变效应的 Rotta 式回归各向同性闭合以及柯尔莫哥洛夫的湍流级联理论，则 Pr(t)-R(i) 关系可以仅从动量和热通量的共谱预算导出。 Kolmogorov 与 Kolmogorov-Obukhov-Corrsin 唯象常数的比率，以及与产生式各向同性相关的常数（其值 (= 3/5) 已根据快速畸变理论预测）解释了所有宏观非线性。
In stably stratified turbulent flows, the mixing efficiency associated with eddy diffusivity for heat, or equivalently the turbulent Prandtl number (Pr(t)), is fraught with complex dynamics originating from the scalewise interplay between shear generation of turbulence and its dissipation by density gradients. A large corpus of data and numerical simulations agree on a near-universal relation between Pr(t) and the Richardson number (R(i)), which encodes the relative importance of buoyancy dissipation to mechanical production of turbulent kinetic energy. The Pr(t)-R(i) relation is shown to be derivable solely from the cospectral budgets for momentum and heat fluxes if a Rotta-like return to isotropy closure for the pressure-strain effects and Kolmogorov's theory for turbulent cascade are invoked. The ratio of the Kolmogorov to the Kolmogorov-Obukhov-Corrsin phenomenological constants, and a constant associated with isotropization of the production whose value (= 3/5) has been predicted from Rapid Distortion Theory, explain all the macroscopic nonlinearities.