The Scalar Gradient Alignment Statistics of Flame Kernels and its Modelling Implications for Turbulent Premixed Combustion
The Scalar Gradient Alignment Statistics of Flame Kernels and its Modelling Implications for Turbulent Premixed Combustion
复制标题
DOI：
10.1007/s10494-010-9250-y
复制
发表时间：
2010-02
期刊：
影响因子：
--
通讯作者：
N. Chakraborty;J. Rogerson;N. Swaminathan
中科院分区：
文献类型：
--
作者：
N. Chakraborty;J. Rogerson;N. Swaminathan
基于衰减湍流条件下不同初始半径的湍流预混火焰核的三维直接数值模拟（DNS）数据，研究了平均火焰曲率对反应进程变量梯度的影响。一个统计平面火焰也被认为是为了比较从内核获得的结果与火焰的平均曲率为零。结果表明，膨胀率效应随着核半径的减小而减小，这是由于在正弯曲区域热量散焦的缘故。这引起的反应进展的程度降低可变梯度对齐与最广泛的主应变速率与减小内核半径。在标量耗散率输运方面研究了与局部应变率对齐的统计的建模影响。一种新的建模方法的标量湍流相互作用项的平均标量耗散的传输方程中的贡献，建议解决的膨胀率的火焰核和湍流应变的小长度尺度在湍流与小火焰核相互作用的减小值的影响。新模型的性能是令人满意的，而比较DNS的结果。膨胀的贡献和合并的化学反应和分子耗散的贡献，最初提出的统计平面火焰的平均标量耗散的运输，现有的模型被发现令人满意地预测湍流火焰内核的相应数量。
The effects of mean flame curvature on reaction progress variable gradient,, alignment with local turbulent strain rate are studied based on three-dimensional Direct Numerical Simulation (DNS) data of turbulent premixed flame kernels with different initial radii under decaying turbulence. A statistically planar flame is also considered in order to compare the results obtained from the kernels with a flame of zero mean curvature. It is found that the dilatation rate effects diminish with decreasing kernel radius due to defocusing of heat in the positively curved regions. This gives rise to a decrease in the extent of reaction progress variable gradient alignment with most extensive principal strain rate with decreasing kernel radius. The modelling implications of the statistics of the alignment ofwith local strain rate have been studied in terms of scalar dissipation rate transport. A new modelling methodology for the contribution of the scalar-turbulence interaction term in the transport equation for the mean scalar dissipation is suggested addressing the reduced effects of dilatation rate for flame kernels and the diminished value of turbulent straining at the small length scales at which turbulence interacts with small flame kernels. The performance of the new models is found to be satisfactory while comparing to DNS results. The existing models for the dilatation contribution and the combined chemical reaction and molecular dissipation contributions to the transport of mean scalar dissipation, which were originally proposed for statistically planar flames, are found to satisfactorily predict the corresponding quantities for turbulent flame kernels.