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Analysis of subgrid scale modeling approaches for large-eddy simulation of turbulent mixing in spatially developing round jets.

机译：在空间发展的圆形射流中对大涡模拟湍流混合的亚网格规模建模方法进行分析。

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摘要

This work involves large eddy simulations (LES) of passive scalar mixing in a round, turbulent jet. We study the effects of resolution on the resulting LES velocity and scalar concentration fields, and focus on the interaction between the modeled, subgrid, and resolved-scale quantities. The simulations are performed in spherical coordinates for Reynolds number Re d = 5,000 at three levels of grid resolution, and for Red = 10,000 at a single resolution level. Throughout this work, the LES-filtered momentum equations are closed using a dynamic Smagorinsky model for the SGS stress.;In the first part of this study, the LES-filtered scalar transport equation is closed using both the dynamic eddy diffusivity and dynamic mixed models for the SGS scalar flux. The mean velocity and scalar concentration fields and jet scaling parameters are accurately reproduced by the LES on all grid systems used. However, there are some variations observed in the mean quantities at different levels of resolution that suggest a non-monotonic influence of subgrid parameters on the resolved LES fields.;The contribution from the SGS model is evaluated by comparing distributions of the modeled subgrid stress and scalar flux components, as well as the SGS and molecular dissipation of resolved-scale fluctuations, at different levels of resolution. Overall, the contribution from the SGS model is observed to increase as the grid is coarsened, indicating as expected that more of the smaller-scale turbulent motions are represented by models at lower levels of resolution.;In the second part of this study, we investigate the effects of different modeling approaches for the SGS scalar flux. The scalar flux models evaluated in this work include, in addition to the eddy diffusivity and mixed models, the recently proposed dynamic structure and multi-fractal models. Resulting mean and fluctuating resolved concentration fields predicted by the multi-fractal model are in close agreement with those predicted by the eddy diffusivity and mixed models, which also show good agreement with available experimental results. The concentration fields predicted by the dynamic structure model differ noticeably from those for the other models in this study, particularly for fluctuating quantities. Analyses of the SGS scalar flux components show that the SGS scalar flux is overpredicted by the dynamic structure model compared to the other models, which may explain some of these trends observed in the resolved and fluctuating concentration fields. The results suggest that model performance, as assessed through the resolved-scale simulation results, is significantly more sensitive to scalar energy transfer across the resolved scale than to the structural details of model formulation.
机译：这项工作涉及在圆形湍流射流中进行被动标量混合的大型涡流模拟（LES）。我们研究了分辨率对产生的LES速度和标量浓度场的影响，并着重于建模量，子网格量和分辨规模量之间的相互作用。对于球形分辨率的三个级别，在雷诺数Re d = 5,000的球形坐标中执行模拟，而在单个分辨率级别的Red = 10,000的球形坐标中进行仿真。在整个工作中，使用动态Smagorinsky模型对SGS应力封闭LES滤波的动量方程。在本研究的第一部分中，使用动态涡流扩散率模型和动态混合模型封闭LES滤波的标量输运方程。用于SGS标量通量。 LES在所有使用的网格系统上准确地再现了平均速度和标量浓度场以及射流缩放参数。但是，在不同分辨率级别上观察到的平均数量存在一些变化，表明亚网格参数对解析的LES场具有非单调影响。通过比较建模的亚网格应力和应力分布，评估了SGS模型的贡献。在不同分辨率下，标量通量分量以及SGS和分辨尺度波动的分子耗散。总体而言，观察到SGS模型的贡献随着网格的粗化而增加，这表明低分辨率级别的模型代表了更多的小尺度湍流运动。；在本研究的第二部分，我们研究不同建模方法对SGS标量通量的影响。在这项工作中评估的标量通量模型除了涡流扩散率和混合模型外，还包括最近提出的动态结构和多重分形模型。多重分形模型预测的平均和波动分辨浓度场与涡流扩散率模型和混合模型预测的场均吻合，也与现有实验结果吻合良好。动态结构模型预测的浓度场与本研究中其他模型的浓度场明显不同，尤其是在波动量方面。对SGS标量通量分量的分析表明，与其他模型相比，动态结构模型对SGS标量通量进行了过度预测，这可能解释了在解析的和波动的浓度场中观察到的某些趋势。结果表明，通过可分辨规模的模拟结果评估的模型性能，对跨可分辨规模的标量能量转移比对模型制定的结构细节更加敏感。

著录项

  • 作者

    Sun, Olivia S.;

  • 作者单位

    The Johns Hopkins University.;

  • 授予单位 The Johns Hopkins University.;
  • 学科 Engineering Mechanical.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 206 p.
  • 总页数 206
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 机械、仪表工业;
  • 关键词

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