DG/FV 混合方法因其具有紧致性、易于推广至高阶及相比同阶 DGM 计算量、存储量小等优点,已成功应用于一维/二维标量方程和 Euler 方程的求解。在此基础上,将该方法推广于二维三角形/矩形混合网格上的 Navier-Stokes 方程数值模拟,将格式形式精度提高至4~5阶。物理量的空间重构及离散使用 DG/FV 混合重构方法;无粘通量计算采用 Roe 格式;粘性通量计算采用 BR2格式;时间方向离散采用高阶显式 R-K 方法或隐式方法。利用该方法计算了有解析解的 Couette 流动问题以验证几种格式的数值精度阶,并计算了层流平板流动和定常、非定常圆柱绕流问题等经典算例。计算结果表明 DG/FV 混合方法达到了设计的精度阶,在较粗的网格上亦能得到高精度的计算结果;定性分析和数值结果表明相比同阶 DG 方法单步计算量减少约40%。
A concept of ‘static reconstruction’and ‘dynamic reconstruction’had been intro-duced for higher-order (third-order and higher)numerical methods in our previous work.Based on this concept,a class of hybrid DG/FV methods had been developed for the scalar equations and Euler equations on triangular and Cartesian/triangular hybrid grids.In this paper,the hybrid DG/FV methods are extended to 2D Navier-Stokes equations on triangular and Cartesian/triangu-lar hybrid grids.The BR2 scheme is employed to discretize the viscous terms.The numerical ac-curacy is validated by some typical test cases,including the Couette flow,laminar flows over a plate and a cylinder.The accuracy study shows that the hybrid DG/FV method achieves the de-sired order of accuracy,and they can capture the flow structure accurately.Qualitative analysis and numerical applications demonstrate that they can reduce the CPU time greatly than the tradi-tional DG method with the same order of accuracy.