Effects of subgrid-scale modeling on Lagrangian statistics in large-eddy simulation
Effects of subgrid-scale modeling on Lagrangian statistics in large-eddy simulation
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DOI：
10.1080/14685240801905360
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发表时间：
2008-01
影响因子：
1.9
通讯作者：
Yue Yang;G. He;Lian-Ping Wang
中科院分区：
文献类型：
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作者：
Yue Yang;G. He;Lian-Ping Wang
大涡模拟（LES）湍流输运过程的应用需要准确预测流场的拉格朗日统计。然而，在大多数现有的SGS模型中，没有明确考虑拉格朗日统计。在本文中，我们专注于SGS建模的影响，拉格朗日统计在LES范围从统计确定单粒子色散对色散和多粒子色散。从直接数值模拟（DNS）和采用谱涡粘性模型的大涡模拟中提取了均匀各向同性湍流的拉格朗日统计量。对于长期单粒子弥散的情况，研究表明，与DNS相比，LES高估了拉格朗日速度相关的时间尺度，但低估了拉格朗日速度波动。这两种效应往往相互抵消，从而导致长期湍流弥散系数的准确预测。不同于单粒子的分散，LES倾向于低估显着的粒子对和多粒子的相对分散率，当初始的分离距离小于最小分辨率的规模，由于缺乏次网格的波动。通过湍流闭合理论的理论分析，进一步证实了LES在拉格朗日速度相关时间尺度上的过度预测。
The application of large-eddy simulation (LES) to turbulent transport processes requires accurate prediction of the Lagrangian statistics of flow fields. However, in most existing SGS models, no explicit consideration is given to Lagrangian statistics. In this paper, we focus on the effects of SGS modeling on Lagrangian statistics in LES ranging from statistics determining single-particle dispersion to those of pair dispersion and multiparticle dispersion. Lagrangian statistics in homogeneous isotropic turbulence are extracted from direct numerical simulation (DNS) and the LES with a spectral eddy-viscosity model. For the case of longtime single-particle dispersion, it is shown that, compared to DNS, LES overpredicts the time scale of the Lagrangian velocity correlation but underpredicts the Lagrangian velocity fluctuation. These two effects tend to cancel one another leading to an accurate prediction of the longtime turbulent dispersion coefficient. Unlike the single-particle dispersion, LES tends to underestimate significantly the rate of relative dispersion of particle pairs and multiple-particles, when initial separation distances are less than the minimum resolved scale due to the lack of subgrid fluctuations. The overprediction of LES on the time scale of the Lagrangian velocity correlation is further confirmed by a theoretical analysis using a turbulence closure theory.