A-priori Direct Numerical Simulation assessment of models for generalized sub-grid scale turbulent kinetic energy in turbulent premixed flames
A-priori Direct Numerical Simulation assessment of models for generalized sub-grid scale turbulent kinetic energy in turbulent premixed flames
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DOI：
10.1016/j.compfluid.2017.05.028
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发表时间：
2017-09
影响因子：
2.8
通讯作者：
M. Klein;C. Kasten;N. Chakraborty
中科院分区：
文献类型：
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作者：
M. Klein;C. Kasten;N. Chakraborty
湍流预混燃烧建模背景下大涡模拟 (LES) 的保真度取决于未解析尺度上发生的湍流和化学反应之间的复杂耦合。尽管燃烧系统的 LES 越来越受欢迎，但次网格尺度 (SGS) 应力的闭合大多是在假设恒定密度流的情况下推导出来的。与未闭合标量通量类似，SGS 应力的行为取决于热释放和湍流之间的平衡，最近的研究表明，当未正确考虑应力张量的各向同性部分时，应力张量可能会发生反梯度传递 (CGT)。这导致从涡粘型模型获得的预测与从直接数值模拟 (DNS) 获得的应力之间存在负相关性。在目前的工作中，详细考虑了与广义亚网格尺度动能密切相关的应力张量各向同性部分的建模。为此，使用具有不同全局路易斯数和热释放参数值的湍流统计平面火焰的先验 DNS 分析来分析 SGS 膨胀效应和未解决的速度波动之间的相互作用。众所周知的广义亚网格尺度动能模型已在湍流预混燃烧的背景下进行了评估，并对其行为提供了详细的物理解释。此外，SGS 膨胀率对 SGS 应力各向异性的影响已使用 Lumley 三角形的变体突出显示。
The fidelity of Large Eddy Simulation (LES) in the context of turbulent premixed combustion modelling depends on the complex coupling between turbulence and chemical reactions occurring at the unresolved scale. Although LES of combustion systems is becoming increasingly popular, the closures for sub-grid scale (SGS) stresses have mostly been derived assuming constant density flows. Similar to the unclosed scalar flux, the behaviour of the SGS stresses depends on the balance between heat release and turbulence, and it has been shown recently that counter-gradient transport (CGT) can occur for the stress tensor when the isotropic part of the stress tensor is not properly accounted for. This leads to a negative correlation between the predictions obtained from an eddy viscosity type model and the stresses obtained from Direct Numerical Simulation (DNS). In the present work the modelling of the isotropic part of the stress tensor, closely related to the generalised sub-grid scale kinetic energy, is considered in detail. To this end the interplay between SGS dilatation effects and unresolved velocity fluctuations is analysed usinga-prioriDNS analysis of turbulent, statistically planar flames with different values of global Lewis number and heat release parameter. Well-known models for generalised sub-grid scale kinetic energy have been assessed in the context of turbulent premixed combustion and detailed physical explanations for their behaviour have been provided. Further, the effects of SGS dilatation rate on the anisotropy of the SGS stresses have been highlighted using a variant of the Lumley triangle.