低密度流体界面不稳定性大涡模拟

采用拉伸涡亚格子尺度应力模型对湍流输运中的亚格子作用项进行模式化处理，发展了适用于可压多介质黏性流动和湍流的大涡模拟方法和代码MVFT（multi-viscous flow and turbulence）。利用MVFT代码对低密度流体界面不稳定性及其诱发的湍流混合问题进行了数值模拟。详细分析了扰动界面的发展，流场中冲击波的传播、相互作用、湍流混合区边界的演化规律，以及流场瞬时密度和湍动能的分布和发展。数值模拟获得的界面演化图像和流场中波系结构与实验结果吻合较好。三维和二维模拟结果的比较显示，两者得到的扰动界面位置、波系及湍流混合区边界基本一致，只是后期的界面构型有所不同，这也正说明湍流具有强三维效应。

Large-eddy simulation of interface instability of low-density fluids

The subgrid-scale (SGS) turbulence transport terms  were modeled by using the stretched-vortex SGS stress model and a large-eddy simulation (LES) code MVFT was developed to investigate the multi-viscous-flow and turbulence problems. Then the interface instability and its induced turbulent mixing of the low-density fluids were simulated numerically by the MVFT code. The simulated images were compared with the experimental results and the detailed analyses were carried out in the following aspects: the development of the perturbed interfaces, the propagations of the shock waves in the flow field and their interactions, the evolutions of the turbulent mixing zone edges, and the instantaneous density and turbulent kinetic energy of the flow filed. Comparisons show that the obtained numerical images for the interface evolutions and the wave structures in the flow field are consistent with the experimental results. And the three-dimensionally simulated results are in agreement with the two-dimensionally simulated ones, which including the positions of the perturbed interfaces, the waves and the turbulent mixing zone edges. Only the two-dimensional simulated images for the the configurations of the perturbed interfaces in the later stage are different from the three-dimensionally simulated results. At the same time, the numerical simulations explain that the turbulent flows have strong three dimensional effects.