Effects of subgrid-scale modeling on time correlations in large eddy simulation
Effects of subgrid-scale modeling on time correlations in large eddy simulation
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DOI：
10.1063/1.1483877
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发表时间：
2002-07-01
影响因子：
4.6
通讯作者：
Wang, LP
中科院分区：
文献类型：
--
作者：
He, GW;Rubinstein, R;Wang, LP
人们正在积极研究大涡模拟（LES）中未解析的亚网格尺度（SGS）运动对解析尺度能量平衡的影响，因为对解析尺度和未解析尺度之间的能量传递进行建模对于构建准确的SGS模型至关重要。但子网格尺度不仅会改变能量平衡，还会导致解析尺度的时间去相关。这种效应在可预测性问题和湍流声辐射评估等应用中的重要性激发了目前 SGS 建模对湍流时间相关性影响的研究。本文将直接数值模拟 (DNS) 评估的各向同性均匀湍流中的两点两次欧拉速度相关性与使用标准谱涡粘性的 LES 评估的相关性进行了比较。事实证明，用速度场的空间傅立叶分解来表达两点相关性是很方便的。 LES 场比 DNS 场更加连贯：它们的时间相关性在所有解析的运动尺度上衰减得更慢，并且它们的积分尺度和微尺度都比 DNS 场大。单独的过滤并不造成这种效果：在傅里叶表示中，过滤后的 DNS 字段的时间相关性与 DNS 字段本身的时间相关性相同。简要讨论了通过在模型中包含随机力来对未解决的运动尺度的去相关效应进行建模的可能性。该结果可应用于利用 LES 计算各向同性均匀湍流中的声源问题。 (C) 2002 年美国物理研究所。
The effects of the unresolved subgrid-scale (SGS) motions on the energy balance of the resolved scales in large eddy simulation (LES) have been investigated actively because modeling the energy transfer between the resolved and unresolved scales is crucial to constructing accurate SGS models. But the subgrid scales not only modify the energy balance, they also contribute to temporal decorrelation of the resolved scales. The importance of this effect in applications including the predictability problem and the evaluation of sound radiation by turbulent flows motivates the present study of the effect of SGS modeling on turbulent time correlations. This paper compares the two-point, two-time Eulerian velocity correlation in isotropic homogeneous turbulence evaluated by direct numerical simulation (DNS) with the correlations evaluated by LES using a standard spectral eddy viscosity. It proves convenient to express the two-point correlations in terms of spatial Fourier decomposition of the velocity field. The LES fields are more coherent than the DNS fields: their time correlations decay more slowly at all resolved scales of motion and both their integral scales and microscales are larger than those of the DNS field. Filtering alone is not responsible for this effect: in the Fourier representation, the time correlations of the filtered DNS field are identical to those of the DNS field itself. The possibility of modeling the decorrelating effects of the unresolved scales of motion by including a random force in the model is briefly discussed. The results could have applications to the problem of computing sound sources in isotropic homogeneous turbulence by LES. (C) 2002 American Institute of Physics.