激波反射对扰动界面湍流混合区影响的数值分析

发展三维可压缩多介质黏性流动和湍流流动的大涡数值模拟方法MVFT3D,对Poggi等人进行的重流体冲击加载轻流体激波管界面不稳定性实验进行数值模拟,通过Vreman SGS应力模型模拟小尺度运动对大尺度运动的影响,运用统计方法分析湍动能特征。计算结果显示,激波多次加载下扰动界面不稳定性及其诱发的湍流混合是一个非常复杂的发展演化过程,在反射激波第一次加载前湍流混合区宽度增长缓慢,湍动能按时间和空间的1.3次幂指数规律衰减,再加载后湍流混合区宽度非线性增长加快,湍动能强度迅速增强后再逐渐递减,而后期的流场则出现明显的气泡竞争现象。计算给出两次再加载的湍流混合区宽度与实验测试结果吻合,第一次再加载前湍动能随时间和空间1.3次幂指数衰减规律与Mohamed和Larue的研究结论一致。数值模拟再现了实验观察到的激波多次加载过程并描述了湍流混合区发展演化的基本物理特征,检验了数值方法和计算程序。

Numerical analyse of the turbulence mixing of re-shocks with a perturbation interface

Three dimensional large eddy simulation method MVFT3D for compressible multi-viscous flow and turbulent flow is developed, and applied to simulate the shock tube experiment of SFe inci- dent on air performed by Poggi et al. The effects of small scale motions on large scales are represented by Vreman SGS stress model, and the characteristics of turbulent kinetic energy are analysed by statistics. It is shown that it is a very complex developing process for a perturbated interfacial instability and it induces the turbulent mixing under multiple shock accelerations, the mixing-zone width is growing slowly before the re-shock accelerating firstly, turbulent kinetic energy decays following the 1.3 power law of time and space, and after the re-shock, the mixing-zone width is growing quickly, the strength of turbulent kinetic energy enhances rapidly and then weakens gradually, the phenomenon of bubble competition appears clearly at late times. The computational mixing-zone width under double re-shocks has agreed well with experimental result, the decaying law of the turbulent kinetic energy is consisitent with Mohamed and Larue＇s investigation, following the 1.3 power law at time and space before the first re-shock. The multiple shock accelerating process is reproduced by simulation, and the basic physical characteristic of the mixing-zone evolution is also described, the numerical method and program are vaildated.