In order to investigate the influence of combustion-induced thermal expansion on turbulent flow within a premixed flame brush, a new method is introduced. The method consists in analyzing structure functions of the velocity field, which characterize velocity difference in two points A and B, with the structure functions being conditioned to various events; (i) unburned reactants in both points, (ii) combustion products in both points, (iii) intermediate states of the mixture in both points, (iv) the reactants in one point and the products in another point, (v) the reactants in one point and an intermediate state in another point, and (vi) the products in one point and an intermediate state in another point. Such structure functions and relevant probabilities are defined in the paper. Subsequently, the structure functions and the probabilities are extracted from Direct Numerical Simulation (DNS) data obtained from two statistically 1D, planar, fully-developed, weakly turbulent, premixed flames characterized by two significantly different (7.53 and 2.50) density ratios, with all other things being approximately equal. Obtained results indicate that (i) the conditioned structure functions differ significantly from the mean structure functions and (ii) the newly introduced approach could convey information important for understanding fundamentals of flame–turbulence interaction and finding issues that require further research. In particular, application of the approach to the aforementioned DNS data shows that the combustion-induced thermal expansion substantially affects small-scale two-point velocity statistics in the incoming constant-density turbulent flow of unburned reactants within a premixed flame brush.

为了研究燃烧引起的热膨胀对预混合火焰刷内湍流的影响，引入了一种新方法。该方法在于分析速度场的结构函数，该结构函数表征了两个点A和B的速度差，并且结构函数受各种事件的影响。（i）两点均未燃烧的反应物，（ii）两点均产生燃烧产物，（iii）两点均处于混合物的中间状态，（iv）一个点处的反应物而另一点处的产物，（v）反应物在一个点上处于中间状态而在另一点上处于中间状态，以及（vi）在一个点上的产品在另一点上处于中间状态。本文定义了此类结构函数和相关概率。随后，结构函数和概率是从直接数值模拟（DNS）数据中提取的，DNS数据是从两个统计的1D平面，平面，完全展开，弱湍流的预混火焰中获得的，这些火焰的特征是两个显着不同的密度比（7.53和2.50），以及其他所有特性大致相等。获得的结果表明：（i）条件结构函数与平均结构函数显着不同；（ii）新引入的方法可以传达对理解火焰-湍流相互作用的基本原理以及发现需要进一步研究的问题很重要的信息。尤其是，