An efficient compressible Euler equation solver for vortex-dominated flows is presented based on the adaptive hybrid Cartesian mesh and vortex identifying method.For most traditional grid-based Euler solvers,the exces...An efficient compressible Euler equation solver for vortex-dominated flows is presented based on the adaptive hybrid Cartesian mesh and vortex identifying method.For most traditional grid-based Euler solvers,the excessive numerical dissipation is the great obstruction for vortex capturing or tracking problems.A vortex identifying method based on the curl of velocity is used to identify the vortex in flow field.Moreover,a dynamic adaptive mesh refinement(DAMR)process for hybrid Cartesian gird system is employed to track and preserve vortex.To validate the proposed method,a single compressible vortex convection flow is involved to test the accuracy and efficiency of DAMR process.Additionally,the vortex-dominated flow is investigated by the method.The obtained results are shown as a good agreement with the previous published data.展开更多
A hybrid Cartesian structured grid method is proposed for solving moving boundary unsteady problems. The near body region is discretized by using the body-fitted structured grids, while the remaining computational dom...A hybrid Cartesian structured grid method is proposed for solving moving boundary unsteady problems. The near body region is discretized by using the body-fitted structured grids, while the remaining computational domain is tessellated with the generated Cartesian grids. As the body moves, the structured grids move with the body and the outer boundaries of inside grids are used to generate new holes in the outside adaptive Cartesian grid to facilitate data communication. By using the alternating digital tree （ADT） algorithm, the computational time of hole-cutting and identification of donor cells can be reduced significantly. A compressible solver for unsteady flow problems is developed. A cell-centered, second-order accurate finite volume method is employed in spatial discreti- zation and an implicit dual-time stepping low-upper symmetric Gauss-Seidei （LU-SGS） approach is employed in temporal discretization. Geometry-based adaptation is used during unsteady simulation time steps when boundary moves and the flow solution is interpolated from the old Cartesian grids to the new one with inverse distance weigh- ting interpolation formula. Both laminar and turbulent unsteady cases are tested to demonstrate the accuracy and efficiency of the proposed method. Then, a 2-D store separation problem is simulated. The result shows that the hybrid Cartesian grid method can handle the unsteady flow problems involving large-scale moving boundaries.展开更多
为提高多段翼型的网格生成效率和数值模拟精度,发展了一套自适应混合笛卡尔网格(AHCG)生成方法和基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解技术。混合笛卡尔网格由围绕物体几何外形的贴体结构网格和填充流场其他区域...为提高多段翼型的网格生成效率和数值模拟精度,发展了一套自适应混合笛卡尔网格(AHCG)生成方法和基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解技术。混合笛卡尔网格由围绕物体几何外形的贴体结构网格和填充流场其他区域的笛卡尔网格构成,两套网格之间的信息传递由"贡献单元"提供,且"贡献单元"由基于ADT(Alternating digital tree)技术的搜寻方法获得。为更准确地捕捉流场信息,采用了基于流场特征的网格自适应技术。数值模拟结果显示,AHCG方法能够准确且高效地模拟高升力多段翼型绕流问题。展开更多
以可压缩黏性流动的数值模拟为研究背景,发展了一套自适应混合笛卡儿网格(AHCG)方法以及基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解方法.为更好地模拟边界层的黏性流动在近壁面处采用贴体结构网格,剩余计算区域自动生...以可压缩黏性流动的数值模拟为研究背景,发展了一套自适应混合笛卡儿网格(AHCG)方法以及基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解方法.为更好地模拟边界层的黏性流动在近壁面处采用贴体结构网格,剩余计算区域自动生成与之相重叠的笛卡儿网格,并同时发展了基于流场特征的笛卡儿网格自适应技术.结合ADT(alternating digital tree)算法显著减少了网格生成中"挖洞"和"贡献单元"搜索的消耗机时,50万左右的网格数目下,搜索耗时为0.062s,仅为普通遍历方法的1/1 847.通过二维圆柱与两段翼型绕流的数值算例显示,定常AHCG方法能够准确地预测物面压力分布与升阻力系数并且具备处理复杂外形的能力;同时通过二维非定常圆柱绕流问题与NACA0015矩形机翼翼尖尾涡的捕捉算例显示,结合了动态自适应网格加密的非定常AHCG方法尤其适用于旋涡主导流动.展开更多
基金Supported by the National Natural Science Foundation of China(11102179)
文摘An efficient compressible Euler equation solver for vortex-dominated flows is presented based on the adaptive hybrid Cartesian mesh and vortex identifying method.For most traditional grid-based Euler solvers,the excessive numerical dissipation is the great obstruction for vortex capturing or tracking problems.A vortex identifying method based on the curl of velocity is used to identify the vortex in flow field.Moreover,a dynamic adaptive mesh refinement(DAMR)process for hybrid Cartesian gird system is employed to track and preserve vortex.To validate the proposed method,a single compressible vortex convection flow is involved to test the accuracy and efficiency of DAMR process.Additionally,the vortex-dominated flow is investigated by the method.The obtained results are shown as a good agreement with the previous published data.
基金supported partly by the National Basic Research Program of China(″973″Program)(No.2014CB046200)
文摘A hybrid Cartesian structured grid method is proposed for solving moving boundary unsteady problems. The near body region is discretized by using the body-fitted structured grids, while the remaining computational domain is tessellated with the generated Cartesian grids. As the body moves, the structured grids move with the body and the outer boundaries of inside grids are used to generate new holes in the outside adaptive Cartesian grid to facilitate data communication. By using the alternating digital tree （ADT） algorithm, the computational time of hole-cutting and identification of donor cells can be reduced significantly. A compressible solver for unsteady flow problems is developed. A cell-centered, second-order accurate finite volume method is employed in spatial discreti- zation and an implicit dual-time stepping low-upper symmetric Gauss-Seidei （LU-SGS） approach is employed in temporal discretization. Geometry-based adaptation is used during unsteady simulation time steps when boundary moves and the flow solution is interpolated from the old Cartesian grids to the new one with inverse distance weigh- ting interpolation formula. Both laminar and turbulent unsteady cases are tested to demonstrate the accuracy and efficiency of the proposed method. Then, a 2-D store separation problem is simulated. The result shows that the hybrid Cartesian grid method can handle the unsteady flow problems involving large-scale moving boundaries.
文摘为提高多段翼型的网格生成效率和数值模拟精度,发展了一套自适应混合笛卡尔网格(AHCG)生成方法和基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解技术。混合笛卡尔网格由围绕物体几何外形的贴体结构网格和填充流场其他区域的笛卡尔网格构成,两套网格之间的信息传递由"贡献单元"提供,且"贡献单元"由基于ADT(Alternating digital tree)技术的搜寻方法获得。为更准确地捕捉流场信息,采用了基于流场特征的网格自适应技术。数值模拟结果显示,AHCG方法能够准确且高效地模拟高升力多段翼型绕流问题。
文摘以可压缩黏性流动的数值模拟为研究背景,发展了一套自适应混合笛卡儿网格(AHCG)方法以及基于有限体积方法的雷诺数平均Navier-Stokes(RANS)的数值求解方法.为更好地模拟边界层的黏性流动在近壁面处采用贴体结构网格,剩余计算区域自动生成与之相重叠的笛卡儿网格,并同时发展了基于流场特征的笛卡儿网格自适应技术.结合ADT(alternating digital tree)算法显著减少了网格生成中"挖洞"和"贡献单元"搜索的消耗机时,50万左右的网格数目下,搜索耗时为0.062s,仅为普通遍历方法的1/1 847.通过二维圆柱与两段翼型绕流的数值算例显示,定常AHCG方法能够准确地预测物面压力分布与升阻力系数并且具备处理复杂外形的能力;同时通过二维非定常圆柱绕流问题与NACA0015矩形机翼翼尖尾涡的捕捉算例显示,结合了动态自适应网格加密的非定常AHCG方法尤其适用于旋涡主导流动.
