横向扰动对超声速混合层被动标量混合影响分析

摘要

Numerical studies on a spatially developing supersonic mixing layer were performed by means of large-eddy simulation.Focusing on the effect of transverse forcing on the passive scalar mixing characteristic of mixing layer.The results for the baseline case without external forcing are in agreement with the analytical evidence.Afterwards,the effect of transverse forcing on the scalar structure,scalar thickness and volumetric entrainment ratio of mixing layer were analyzed.Results indicate that the frequency and amplitude of transverse forcing alter the growth rate and entrainment ratio of the passive scalar mixing significantly.High-frequency forcing magnifies the scalar thickness and volumetric entrainment ratio in the near field of mixing layer.However,the growth rate in the far field is increased by the low-frequency forcing.The entrainment ratio is,to be a large extent,dominated by the large-scale eddy entrainment process.The multiple-frequency forcing seems to validly enhance the scalar mixing in supersonic mixing layer.%采用大涡模拟数值计算二维空间发展的超声速混合层，重点分析横向扰动对混合层的标量结构、标量厚度以及标量体积卷吸率的影响。采用理论模型验证了数值方法在计算标量混合特性方面的准确性。结果表明，横向扰动频率和振幅明显影响着混合层的标量增长率和卷吸率。高频扰动增大了混合层近场标量增长率和卷吸率，但是低频扰动改善了混合层远场标量增长率。大尺度涡卷吸过程对混合层标量卷吸率起决定作用。多频扰动有效地增强了超声速混合层的标量混合。