Statistics and Modelling of Turbulent Kinetic Energy Transport in Different Regimes of Premixed Combustion
Statistics and Modelling of Turbulent Kinetic Energy Transport in Different Regimes of Premixed Combustion
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DOI：
10.1007/s10494-010-9312-1
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发表时间：
2011-10-01
影响因子：
2.4
通讯作者：
Cant, R. Stewart
中科院分区：
文献类型：
--
作者：
Chakraborty, Nilanjan;Katragadda, Mohit;Cant, R. Stewart
本文用三维直接数值模拟（DNS）的数据分析了湍流预混火焰中湍流动能输运的统计特性。对于波纹状火焰区域内的火焰，观察到在火焰刷内产生湍流动能。相比之下，对于薄反应区范围内的火焰，已经发现湍流动能通过火焰刷单调衰减。湍流动能耗散率也观察到类似的趋势。在波纹状的火焰制度，它表明，火焰内的平均压力梯度和压力扩张的影响是足以克服粘性耗散的影响，并负责所观察到的增强湍流动能在火焰刷。在薄的反应区制度，平均压力梯度和压力膨胀项的影响是相对弱得多的粘性耗散，导致在整个火焰刷的湍流动能的单调衰减。本文详细分析了湍流动能输运方程各种开项的模拟。现有模型的预测与从DNS数据中提取的相应数量进行比较。基于这种先验DNS评估，识别适当的模型或在必要时提出新模型。结果表明，在湍流标量通量具有反梯度（梯度）性质的地方，湍流动能通量呈现反梯度（梯度）输运。已经提出了一个新的模型的湍流动能的湍流通量，并发现捕获的定性和定量的行为从DNS数据的波纹flamerescent和薄的反应区制度，而不需要调整任何的模型常数。
The statistical behaviour of turbulent kinetic energy transport in turbulent premixed flames is analysed using data from three-dimensional Direct Numerical Simulation (DNS) of freely propagating turbulent premixed flames under decaying turbulence. For flames within the corrugated flamelets regime, it is observed that turbulent kinetic energy is generated within the flame brush. By contrast, for flames within the thin reaction zones regime it has been found that the turbulent kinetic energy decays monotonically through the flame brush. Similar trends are observed also for the dissipation rate of turbulent kinetic energy. Within the corrugated flamelets regime, it is demonstrated that the effects of the mean pressure gradient and pressure dilatation within the flame are sufficient to overcome the effects of viscous dissipation and are responsible for the observed augmentation of turbulent kinetic energy in the flame brush. In the thin reaction zones regime, the effects of the mean pressure gradient and pressure dilatation terms are relatively much weaker than those of viscous dissipation, resulting in a monotonic decay of turbulent kinetic energy across the flame brush. The modelling of the various unclosed terms of the turbulent kinetic energy transport equation has been analysed in detail. The predictions of existing models are compared with corresponding quantities extracted from DNS data. Based on this a-priori DNS assessment, either appropriate models are identified or new models are proposed where necessary. It is shown that the turbulent flux of turbulent kinetic energy exhibits counter-gradient (gradient) transport wherever the turbulent scalar flux is counter-gradient (gradient) in nature. A new model has been proposed for the turbulent flux of turbulent kinetic energy, and is found to capture the qualitative and quantitative behaviour obtained from DNS data for both the corrugated flamelets and thin reaction zones regimes without the need to adjust any of the model constants.