二维混合层拟序结构的直接数值模拟

DIRECT NUMERICAL SIMULATION OF COHERENT STRUCT-URES IN TWO-DIMENSIONAL MIXING LAYER

本文是在文[1]的基础上,引用Cain等人(1981)提出的映射函数将无穷远的边界变换到有限距离处,用伪谱方法对N-S方程组进行直接数值模拟,研究时间发展的二维混合层的不稳定性,再现了大涡的卷起,涡对的合并与撕裂以及三个涡、四个涡之间的相互作用过程,并将过程进行了动态显示。

This paper is to investigate the coherent structures of two-dimensionatemporally evolving mixing layer by direct numerical simulation (DNS) of Navier-Stokes equations using pseudospectral method. To avoid imaging error, mapping function designed by Cain et al. is used here to transform the original infinite region to a finite domain.The approach explains numerically the important role of fundamental perturbation wave-and its subharmonic wave in the formation, development and interaction of coherent structures in mixing layer. The results demonstrate vividly the process of the rolling up, pairing and shedding of large vortices and interaction between three, four large-scale structures. It also shows the existing and evolving of coherent structures are the main mechanism of growing and entrain-merit of mixing layer.