气体动理学格式与多尺度流动模拟

摘要

介绍了气体动理学格式(GKS)的基本构造原理及其在两种典型多尺度流动模拟中的应用.GKS利用介观BGK方程的跨尺度演化解来构造网格界面上的数值通量,从而发展出能随计算网格尺度变化自动切换物理模型的多尺度方法.对湍流这种宏观多尺度流动,发展了高精度GKS方法并成功用于低雷诺数湍流的直接数值模拟;为实现对高雷诺数湍流的高效精细模拟,基于拓展BGK方程和已有的RANS,LES模型建立了新型多尺度模拟框架.对跨流域稀薄流动,发展了适合大规模并行的三维统一气体动理学格式(UGKS),并建立了适合轴对称稀薄流动的UGKS.研究表明,GKS在多尺度流动高效模拟中的优异性能,具有很好的发展前景.%The fundamental features of Gas Kinetic Scheme (GKS) and its application in two typical multiscale flows are introduced.In GKS the multiscale general solution of BGK equation is used to construct the numerical flux at a cell interface and then the multiscale method is developed which can achieve smooth transition between different physical models according to computational cell size.To simulate the macroscopic multiscale flow,for example, turbulence,the high-order accurate GKS is developed and successfully applied in the direct numerical simulation of low-Reynolds-number turbulence.For detailed simulation of high-Reynolds-number turbulence with high efficiency,a new multiscale framework is proposed based on the expanded BGK equation and existing RANS and LES models.To predict rarefied gas flow,the unified GKS is extended to three-dimensional curvilinear mesh and parallelized for large-scale computing.A UGKS for axisymmetric rarefied flow is also proposed.The present study demonstrates the GKS has an excellent performance and a promising prospect for high efficiency computation of multiscale flows.