A-priori testing of an eddy viscosity model for the density-weighted subgrid scale stress tensor in turbulent premixed flames
A-priori testing of an eddy viscosity model for the density-weighted subgrid scale stress tensor in turbulent premixed flames
复制标题
湍流预混火焰中密度加权亚网格尺度应力张量涡粘模型的先验测试
DOI：
10.1007/s00348-009-0799-y
复制
发表时间：
2010
影响因子：
2.4
通讯作者：
A. Leipertz
中科院分区：
文献类型：
--
作者：
S. Pfadler;F. Beyrau;F. Dinkelacker;A. Leipertz
在本研究中，我们报道了直接测量湍流预混火焰中的密度加权亚网格尺度（SGS）应力张量。在大涡模拟（LES）中，这种未解析张量通常使用涡粘性方法进行建模。除了直接测量外，我们还对Smagorinsky提出的常用涡流粘度模型进行了纯粹的基于实验的先验测试。针对两种紊流预混v型甲烷-空气火焰，对直接测量的SGS应力张量与Smagorinsky的涡动黏度模型的相关性进行了统计分析。该测量策略基于双平面立体piv技术的应用，可以在两个平行平面上测量三维流场。这样就可以确定三个方向上的速度和速度梯度。在这里，矢量分辨率达到118 μm。对于先验测试，数据要经过空间过滤过程，该过程再现了过滤函数在LES中的应用。应用该空间平均后进行速度梯度的计算。除速度场外，还通过火焰燃烧区和未燃烧区之间的示踪粒子数密度的明显变化推断出火焰锋面位置。这有助于对密度加权SGS应力张量的所有分量进行直接的单次评估。此外，可以确定与这些项相关的模型表达式，这是在静态Smagorinsky模型的第一个研究中完成的。这样，基于瞬时局部评价程序的直接测量应力项与模拟应力项之间的瞬时局部比较就成为可能。描述了测量过程，并给出了初步结果并进行了讨论。它们表现出静态形式的Smagorinsky模型（固定Smagorinsky常数）的相当差的性能。我们未来的目标是使用直接测量的SGS数据与更先进的模型进行先验比较。
In this study, we report on the direct measurement of the density-weighted subgrid scale (SGS) stress tensor in turbulent premixed flames. In large-eddy simulations (LES), this unresolved tensor is typically modelled using eddy viscosity approaches. Additionally to the direct measurement, we provide a pure experimentally based a-priori test of the commonly used eddy viscosity model suggested by Smagorinsky. For two turbulent premixed V-shaped methane–air flames, a statistical analysis is presented where the correlation between the directly measured SGS stress tensor and the eddy viscosity model following Smagorinsky is tested. The measurement strategy is based on the application of a dual-plane stereo-PIV technique which enables the measurement of the 3D flow field in two parallel planes. This allows the determination of velocities as well as velocity gradients in all three directions. Here, a vector resolution of 118 μm was achieved. For a priori testing, the data are subjected to a spatial filtering procedure that reproduces the application of the filter function in LES. The calculation of velocity gradients is performed after the application of this spatial averaging. Additionally to the velocity field, the flame front position is deduced from the clearly observable step in the tracer particle number density between burnt and unburnt regions of the flame. This facilitates the direct single-shot-based evaluation of all components of the density-weighted SGS stress tensor. Additionally, the model expressions related to these terms can be determined, which is done in this first study for the static Smagorinsky model. With that, the instantaneous local comparison between directly measured stress terms and modelled terms is possible, based on the instantaneous local evaluation procedure. The measurement procedure is described, and first results are presented and discussed. They show a rather poor performance of the static form of the Smagorinsky model (with fixed Smagorinsky constant). Our future aims are to use the directly measured SGS data for the a-priori comparison with more advanced models.