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首页> 外文期刊>Computers & Fluids >A-priori Direct Numerical Simulation assessment of models for generalized sub-grid scale turbulent kinetic energy in turbulent premixed flames
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A-priori Direct Numerical Simulation assessment of models for generalized sub-grid scale turbulent kinetic energy in turbulent premixed flames

机译：湍流预混火焰中广义子网格稳定动力动能模型的a-priori直接数值模拟评估

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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 using a-priori DNS 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. (C) 2017 Elsevier Ltd. All rights reserved.
机译：湍流预混燃烧建模背景下大型涡流模拟（LES）的保真度取决于湍流和在未解决的规模处发生的湍流和化学反应之间的复杂耦合。尽管燃烧系统的燃烧系统越来越受欢迎，但是假设恒定密度流动的子网格秤（SGS）应力的封闭件主要得到。类似于未休憩的标量通量，SGS应力的行为取决于热释放和湍流之间的平衡，并且最近已经显示了当应力的各向同性部分时，应在应力张量时发生反梯度传输（CGT）张量没有恰当地占据。这导致从涡粘度型模型获得的预测和从直接数值模拟（DNS）获得的应力之间的负相关性。在本工作中，详细考虑了与广义子网格级动能密切相关的应力张力的各向同性部分的建模。为此，使用具有湍流的a-priori dns分析，分析SGS扩张效果和未解决的速度波动之间的相互作用，其具有湍流，统计的平面火焰的不同值，具有不同的全球刘易斯数和热释放参数。在湍流预混燃烧的背景下，已经评估了广义子网格规模动能的众所周知的模型，并提供了对其行为的详细物理解释。此外，使用Lumley三角形的变体突出显示SGS扩张率对SGS应力各向异性的影响。 （c）2017 Elsevier Ltd.保留所有权利。

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