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首页> 外文期刊>European Journal of Mechanics, B. Fluids >Evaluation of non-eddy viscosity subgrid-scale models in stratified turbulence using direct numerical simulations
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Evaluation of non-eddy viscosity subgrid-scale models in stratified turbulence using direct numerical simulations

机译：使用直接数值模拟评估分层湍流中的非涡粘度亚级模型模型

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This research studies the performance of eddy and non-eddy viscosity subgrid-scale (SGS) models using direct numerical simulations (DNS) of stratified turbulence. Nonlinear and modulated gradient models, as the two common non-eddy viscosity SGS parameterizations, are considered. For comparison, the two common eddy-viscosity SGS parameterizations, i.e. the Smagorinsky and dynamic Smagorinsky models, are also considered. Also, two types of test filters the Gaussian and spectral filters are employed to study the performance of these SGS models in stratified turbulence. Our results show that when a Gaussian filter is applied, the SGS fluxes and dissipation rates obtained with the nonlinear and modulated gradient models are very similar to those of the actual SGS motions. On the other hand, the Smagorinsky and dynamic Smagorinsky models yield good results when a spectral filter is applied. The correlation coefficient between the actual and modelled SGS fluxes is very high for the non-eddy viscosity models, and depends on the filter type. Overall, our results suggest that the performance of SGS models depends on the resolution of the buoyancy scale L-b: in order to prevent excessive dissipation around the filter scale Delta(f), the buoyancy scale L-b should be resolved. The resolution of Lb has already been shown as a requirement in large-eddy simulations of stratified turbulence when eddy viscosity SGS models are employed (Khani & Waite, 2014, 2015). However, the importance of the buoyancy scale Lb has not been studied before in non-eddy viscosity SGS models. This research work provides a strong support for the choice of minimum resolved scale for both eddy and non-eddy viscosity SGS parameterizations, including nonlinear and modulated gradient models, in stratified turbulence through a theoretical scale analysis and using DNS data. (c) 2017 Elsevier Masson SAS. All rights reserved.
机译：本研究研究了使用分层湍流的直接数值模拟（DNS）的涡流和非涡粘度亚谱级（SGS）模型的性能。非线性和调制梯度模型，作为两个常见的非涡粘度SGS参数化，被认为是参数化。为了比较，还考虑了两种常见的涡粘度SGS参数化，即Smagorinsky和动态Smagorinsky模型。此外，使用两种类型的测试滤波器高斯和光谱滤波器来研究这些SGS模型在分层湍流中的性能。我们的研究结果表明，当应用高斯滤波器时，使用非线性和调制梯度模型获得的SGS助熔剂和耗散速率与实际SGS运动的SGS助熔剂和耗散速率非常相似。另一方面，SMAGORINSKY和动态SMAGORINSKY模型在施加光谱滤波器时产生良好的结果。对于非涡粘度模型，实际和建模的SGS助熔剂之间的相关系数非常高，并且取决于过滤型。总体而言，我们的结果表明SGS模型的性能取决于浮力量表L-B的分辨率：为了防止过滤量表Δ（F）周围过度耗散，应解决浮力量L-B。当采用涡流粘度SGS模型时，LB的分辨率已经显示为分层湍流的大涡血管模拟（Khani＆Waite，2015,2015）。然而，在非涡粘度SGS模型中之前尚未研究浮力量标LB的重要性。该研究工作提供了强大的支持，对涡流和非涡粘度SGS参数化，包括非线性和调制梯度模型的最小解析规模，通过理论级别分析和使用DNS数据，包括非线性和调制梯度模型。 （c）2017年Elsevier Masson SAS。版权所有。

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