Conditional dissipation of scalars in homogeneous turbulence: Closure for MMC modelling
Conditional dissipation of scalars in homogeneous turbulence: Closure for MMC modelling
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均匀湍流中标量的条件耗散：MMC 建模的闭包
DOI：
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发表时间：
2013
期刊：
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通讯作者：
Andrew P. Wandel
中科院分区：
文献类型：
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作者：
Andrew P. Wandel
虽然任何合理的湍流燃烧模型都能很好地预测平均值和无条件方差，但这些通常不足以对复杂现象（如熄火/重燃）进行精确建模。最近引入了一个额外的标准：与标量的波动有关的条件平均值（条件耗散时标）的耗散时标的准确建模。对被动标量的直接数值模拟（DNS）结果的分析表明，条件耗散时间尺度是积分时间尺度的量级，小于无条件耗散时间尺度。提出了一个模型：条件耗散时标与积分时标成正比。该模型用于多映射条件（MMC）建模的被动标量的情况下，反应标量的情况下，DNS结果相比。结果表明，该模型提高了MMC预测的准确性，从而更紧密地匹配DNS的结果相比，其他湍流燃烧模型使用相对粗糙的空间分辨率。
While the mean and unconditional variance are to be predicted well by any reasonable turbulent combustion model, these are generally not sufficient for the accurate modelling of complex phenomena such as extinction/reignition. An additional criterion has been recently introduced: accurate modelling of the dissipation timescales associated with fluctuations of scalars about their conditional mean (conditional dissipation timescales). Analysis of Direct Numerical Simulation (DNS) results for a passive scalar shows that the conditional dissipation timescale is of the order of the integral timescale and smaller than the unconditional dissipation timescale. A model is proposed: the conditional dissipation timescale is proportional to the integral timescale. This model is used in Multiple Mapping Conditioning (MMC) modelling for a passive scalar case and a reactive scalar case, comparing to DNS results for both. The results show that this model improves the accuracy of MMC predictions so as to match the DNS results more closely using a relatively-coarse spatial resolution compared to other turbulent combustion models.