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首页> 外文会议>IUTAM Symposium on Turbulent Mixing and Combustion, Jun 3-6, 2001, Kingston, Ontario, Canada >CHARACTERISTICS OF SUPERCRITICAL TRANSITIONAL TEMPORAL MIXING LAYERS
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CHARACTERISTICS OF SUPERCRITICAL TRANSITIONAL TEMPORAL MIXING LAYERS

机译：超临界过渡温度混合层的特征

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摘要

Several Direct Numerical Simulation realizations of supercritical, three-dimensional, temporal mixing layers are used to investigate aspects of interest to turbulent combustion. The realizations are based on a model previously developed that accounts for the enlarged transport matrix at supercritical conditions (Soret and Dufour effects), for real gas equations of state, and for variable Schmidt and Prandtl numbers. This model is exercised for two very different sets of binary species, heptaneitrogen and oxygen/hydrogen, to obtain transitional states for mixing layers excited at different perturbation wavelengths. Visualizations of the transitional states show that all layers develop convoluted regions of high density gradient magnitude (HDGM), which result both from the distortion of the initial density stratification boundary and from mixing. The species mass fraction in these HDGM regions is very weakly dependent of the perturbation wavelength. The existence of the HDGM regions, independent of the perturbation wavelength, indicates that they may be a feature of spatial mixing layers, and furthermore have a similar mass fraction composition. Evaluations of the applicability of the assumed PDF method for describing supercritical transitional flows shows that neither the β density nor the Gaussian are appropriate representations of the conserved scalar, and that the PDFs of the partial densities and the temperature are correlated, invalidating the typical model of the reaction rate as the product of the marginal PDFs.
机译：超临界，三维，时间混合层的几种直接数值模拟实现，用于研究湍流燃烧感兴趣的方面。这些实现基于先前开发的模型，该模型考虑了超临界条件（索雷特效应和杜福尔效应）下的扩大的输运矩阵，真实的气体状态方程以及可变的施密特数和普朗特数。对两种非常不同的二元物种（庚烷/氮和氧/氢）使用此模型，以获得过渡态，以混合在不同摄动波长下激发的层。过渡态的可视化显示，所有层都形成了高密度梯度幅度（HDGM）的回旋区，这既是由于初始密度分层边界的扭曲也由于混合造成的。这些HDGM区域中的物质质量分数非常弱地取决于扰动波长。 HDGM区域的存在与扰动波长无关，这表明它们可能是空间混合层的特征，而且具有相似的质量分数组成。对假定的PDF方法用于描述超临界过渡流的适用性进行的评估表明，β密度和高斯都不是守恒标量的适当表示，并且部分密度和温度的PDF相关，从而使模型的典型模型无效。反应速度是边际PDF的乘积。

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