Strain rates normal to approaching iso-scalar surfaces in a turbulent premixed flame
Strain rates normal to approaching iso-scalar surfaces in a turbulent premixed flame
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DOI：
10.1016/j.combustflame.2014.11.034
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发表时间：
2015-05-01
影响因子：
4.4
通讯作者：
Jimenez, Carmen
中科院分区：
文献类型：
--
作者：
Dopazo, Cesar;Cifuentes, Luis;Jimenez, Carmen
采用直接数值模拟（DNS）方法，研究了在输入-输出结构中采用Arrhenius一步化学反应的湍流预混传播火焰的数据集。燃烧发生在“波纹状火焰”状态。热释放导致流动体积膨胀率在大部分计算域上为正，相关的正应变率垂直于等标量表面，并且正应变率或负应变率都与它们相切。凸、凹等值面微元法向传播分别产生拉伸和收缩，叠加切向流应变率效应。等值面的法向传播速度从“新鲜气体”到“热产品”单调增加，这使得两个相邻的等值面更接近：由于化学和分子扩散运输，这种贡献远大于法向流动应变，并增强了混合和化学转化。传统上用切向应变率解释的湍流预混火焰的许多方面可以用正常的来很好地理解。(C)2014燃烧研究所爱思唯尔公司出版All rights reserved.
A Direct Numerical Simulation (DNS) dataset of a turbulent premixed propagating flame with an Arrhenius one-step chemistry in an input-output configuration is examined. Combustion takes place in the 'corrugated flamelets' regime. Heat release causes the flow volumetric dilatation rate to be positive over most of the computational domain, with associated positive strain rates normal to iso-scalar surfaces and both positive or negative strain rates tangent to them. The normal propagation of convex and concave iso-surface infinitesimal area elements produces stretching and reduction, respectively, superposed to tangential flow strain rate effects. The normal propagation speed of iso-surfaces increases monotonically from 'fresh gases' to 'hot products', which draws two adjacent ones closer: this contribution, due to both chemistry and molecular diffusive transport, is much greater than that of the normal flow strain, and enhances mixing and chemical conversion. Many aspects of turbulent premixed flames traditionally explained in terms of tangential strain rates can likely be well understood using the normal ones. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.