大涡模拟超声速两相流混合层的非线性分析

为研究超声速两相流混合机理，采用大涡模拟（LES）方法数值仿真了超声速混合层内液滴两相流流场结构。用二维盒式滤波法处理可压缩气相NS方程，得到亚格子形式的LES控制方程；用轨道模型仿真液滴运动，并用单液滴蒸发模型模拟液滴蒸发过程。利用伪邻近法和互信息量法确定了相空间重构的嵌入维数和时间延迟，对混合层压力时间序列进行了相空间重构。分析了仿真结果中混合层的涡结构特性和液滴对流场的反作用效果，并讨论了混合层失稳过程的非线性特征。发现混合层发展的不同阶段与其系统的非线性特征值密切相关。

Nonlinear Analyse of Large Eddy Simulated Supersonic Two-phase Mixing Layer

The two-phase compressible mixing layer with droplets was calculated by large eddy simulation (LES) for studying the mixing law of supersonic two-phase flow. To get the sub-grid LES equations, the compressible NS equations of gaseous phase were filtered by two-dimensional box-filter function. The droplets phase was simulated by track model, and the evaporation equations of single droplet model were employed to simulate the evaporating course. The phase space for the time series of mixing layer pressure was reconstructed by getting the embedding dimension and time-delay of the phase space reconstruction, in the method of false neighbors and mutual information.The characteristic of eddy and droplets evaporation in mixing layer were analyzed, and more over the nonlinear characteristic of mixing layer instability was discussed. The results show the different developing stages of mixing layer have close-relationship with its nonlinear eigenvalue.