Direct numerical simulation (DNS) results are analysed to investigate the effect of flame–flame interaction on the scalar distribution in a large eddy simulation context. The DNS data consist of turbulent premixed planar flame, V-flame and swirl flame cases with different turbulence and equivalence ratio, and relatively large Damköhler number conditions are considered for the three DNS cases. The volumetric fraction of non-flamelet type reaction zones $\overline{\Phi }$, which are caused by flame–flame interaction (FFI), is identified by the trained neural network. The quantification of scalar PDF mode is carried out by means of the bimodality coefficient. Various scalar PDFs are constructed with different sample volumes of the filter size. The PDFs with high bimodality coefficient samples show clear bimodal distributions, whereas low bimodality coefficient samples show unimodal or plateau distributions. The conditional PDF and conditional average of the bimodality coefficient conditioned based on $\overline{\Phi }$ clearly show negative correlation between these two quantities. These results suggest that the presence of FFI events leads to bimodality loss of the scalar field, even when the Damköhler number is large. Reaction zones with non-bimodal scalar distribution are also found to have very small scalar gradient. Thus, the reaction rate of such reaction zones could be underestimated in flamelet-type modelling. However, such deficit may be straightforwardly complemented additively, for example, by considering a zero-dimensional canonical reactor with the fraction $\overline{\Phi }$.

分析直接数值模拟 (DNS) 结果以研究火焰-火焰相互作用对大涡模拟环境中标量分布的影响。DNS 数据由湍流预混平面火焰、V 型火焰和涡流火焰情况组成，具有不同的湍流和当量比，并且对于三种 DNS 情况考虑了相对较大的 Damköhler 数条件。非火焰型反应区的体积分数$\overline{\Phi }$由火焰-火焰相互作用（FFI）引起，由经过训练的神经网络识别。标量 PDF 模式的量化是通过双峰系数进行的。各种标量 PDF 是用不同的过滤器大小的样本量构建的。具有高双峰系数样本的 PDF 显示出清晰的双峰分布，而低双峰系数样本显示单峰或平台分布。基于条件的双峰系数的条件 PDF 和条件平均值$\overline{\Phi }$清楚地显示这两个量之间的负相关。这些结果表明，即使 Damköhler 数很大，FFI 事件的存在也会导致标量场的双峰损失。还发现具有非双峰标量分布的反应区具有非常小的标量梯度。因此，在火焰型建模中可能会低估此类反应区的反应速率。然而，这种缺陷可以直接加法补充，例如，通过考虑具有分数的零维规范反应器$\overline{\Phi }$.