Gabor mode enrichment in large eddy simulations of turbulent flows
Gabor mode enrichment in large eddy simulations of turbulent flows
复制标题
湍流大涡模拟中的 Gabor 模式富集
DOI：
10.1017/jfm.2020.622
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发表时间：
2020
影响因子：
3.7
通讯作者：
Lele, Sanjiva
中科院分区：
文献类型：
--
作者：
Ghate, Aditya;Lele, Sanjiva
在后验分析的背景下，对大涡模拟（LES）中子滤波尺度运动的湍流富集模型进行了全面评价。本文进一步发展了Ghate & Lele （J.流体力学）首次提出的Gabor模式富集模型。通过分析利用螺线管小尺度速度场进行LES富集的三个关键条件：(a)一致的光谱外推和解决的单点和两点二阶相关的改进；(b)在小尺度上精确捕捉导致时间去相关的流动物理的能力；(c)由粗网格LES和子滤波尺度解析的尺度间空间局域和间歇能量传递的精确表征。我们认为，空间和频谱局域化的Gabor波包为表示准均匀区域内的小尺度湍流提供了最佳基础，尽管精细尺度涡度与大尺度应变的一致性似乎有些过分强调。因此，我们将得到的子滤波尺度解释为由一组空间分散的burger - townsend涡旋引起的尺度，其方向由粗网格LES解析的更大尺度速度梯度决定。对两种高雷诺数流动形态、均匀各向同性湍流和粗糙壁面湍流边界层进行了丰富的粗网格模拟，得到了令人满意的结果。
A turbulence enrichment model for subfilter-scale motions in large eddy simulations (LES) is comprehensively evaluated in the context of a posteriori analysis. The paper further develops the Gabor mode enrichment model first introduced in Ghate & Lele (J. Fluid Mech., vol. 819, 2017, pp. 494–539) by analysing three key requisites of LES enrichment using solenoidal small-scale velocity fields: (a) consistent spectral extrapolation and improvement of resolved single- and two-point second-order correlations; (b) ability to accurately capture the flow physics responsible for temporal decorrelation at small scales; and (c) accurate representation of spatially localized and intermittent interscale energy transfer between scales resolved by the coarse-grid LES and subfilter scales. We argue that the spatially and spectrally localized Gabor wavepackets offer an optimal basis to represent small-scale turbulence within quasi-homogeneous regions, although the alignment of fine-scale vorticity with large-scale strain appears to be somewhat overemphasized. Consequently, we interpret the resulting subfilter scales as those induced by a set of spatially dispersed Burgers–Townsend vortices with orientations determined by the larger scale velocity gradients resolved by the coarse-grid LES. Enrichment of coarse-grid simulations of two high Reynolds number flow configurations, homogeneous isotropic turbulence and a rough-wall turbulent boundary layer show promising results.