高阶精度DG/FV混合方法在二维粘性流动模拟中的推广
Applications of high order hybrid DG/FV methods for 2D viscous flows
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摘要: 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%。Abstract: A concept of 'static reconstruction' and 'dynamic reconstruction' had been introduced 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/triangular hybrid grids. The BR2 scheme is employed to discretize the viscous terms. The numerical accuracy 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 desired 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 traditional DG method with the same order of accuracy.