Influence of the Lewis Number on Effective Strain Rates in Weakly Turbulent Premixed Combustion
Influence of the Lewis Number on Effective Strain Rates in Weakly Turbulent Premixed Combustion
复制标题
弱湍流预混燃烧中路易斯数对有效应变率的影响
DOI：
10.1080/00102202.2017.1398744
复制
发表时间：
2018
影响因子：
1.9
通讯作者：
N. Chakraborty
中科院分区：
文献类型：
--
作者：
C. Dopazo;L. Cifuentes;Dana Alwazzan;N. Chakraborty
摘要本文基于自由传播统计平面湍流预混火焰的三维直接数值模拟数据，分析了整体刘易斯数Le对“有效”法向和切向应变率统计行为的影响，Le = 0.34、0.60、0.80、1.00和1.20。体积扩张率被发现大多是积极的，其幅度增加，减少乐。流动法向应变率主要假设为正值，因此倾向于将相邻的等标量表面拉开，这减小了标量梯度。相比之下，由于垂直于等值面的位移速度的导数而产生的“增加的”法向应变率具有将它们推得更靠近在一起的倾向，并且因此增加标量梯度的幅度。流动和附加的正常应变率之间的平衡沿着平流输送决定标量梯度是增强还是破坏。流体流动拉伸的等值面单元面积随着刘易斯数的减小而增加，并且所增加的切向应变速率呈现出主要为负值，并且由位移速度分量和火焰曲率之间的相关性确定。研究发现，当刘易斯数较小时，湍流火焰呈现出火焰变薄和火焰表面积增大的趋势，并且随着刘易斯数的减小，这种趋势增强。这一行为已详细解释的统计行为的有效法向和切向应变率。
ABSTRACT The influence of the global Lewis number, Le, on the statistical behavior of the “effective” normal and tangential strain rates have been analyzed based on three-dimensional direct numerical simulation data of freely propagating statistically planar turbulent premixed flames with Le = 0.34, 0.60, 0.80, 1.00, and 1.20. The volumetric dilatation rate is found to be mostly positive and its magnitude increases with decreasing Le. The flow normal strain rate predominantly assumes positive values and thus tends to pull adjacent iso-scalar surfaces apart, which reduces scalar gradients. By contrast, the “added” normal strain rate due to derivatives of the displacement speed normal to iso-surfaces has the propensity to push them closer together, and therefore increase the magnitude of scalar gradients. The balance between flow and added normal strain rates along with the advective transport determines whether scalar gradients are enhanced or destroyed. Iso-surface elementary area stretching by the fluid flow increases with decreasing Lewis number, and the added tangential strain rate exhibits predominantly negative values and is determined by the correlation between displacement speed components and flame curvature. It has been found that turbulent flames with small values of Lewis number exhibit flame thinning and high values of the flame surface area and these tendencies strengthen with decreasing Lewis number. This behavior has been explained in detail in terms of the statistical behaviors of effective normal and tangential strain rates.
登录
查看更多内容
DOI：
10.1080/10407782.2016.1257309
发表时间：
2017-01
期刊：
Numerical Heat Transfer, Part A: Applications
影响因子：
--
作者：
U. Allauddin;M. Klein;M. Pfitzner;N. Chakraborty
通讯作者：
U. Allauddin;M. Klein;M. Pfitzner;N. Chakraborty
影响因子：
4.4
作者：
Chakraborty, Nilanjan;Cant, R. S.
通讯作者：
Cant, R. S.
影响因子：
4.4
作者：
D. Butz;Yuan Gao;A. Kempf;N. Chakraborty
通讯作者：
D. Butz;Yuan Gao;A. Kempf;N. Chakraborty
使用非统一路易斯数简化预混合火焰的分段统计。
DOI：
10.1103/physreve.89.033015
发表时间：
2014
期刊：
Physical review. E, Statistical, nonlinear, and soft matter physics
影响因子：
--
作者：
Chakraborty N
通讯作者：
Chakraborty N
影响因子：
4.6
作者：
N. Chakraborty;R. Cant
通讯作者：
N. Chakraborty;R. Cant