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并行化六面体占优高阶曲网格生成方法

PARALLEL GENERATION OF HEXAHEDRAL-DOMINANT HIGH ORDER CURVILINEAR MESH

  • 摘要: 高阶方法在湍流、燃烧、气动噪声数值模拟等领域具有重要的应用价值. 直网格在应用于高阶方法时可能会产生非物理解, 采用高阶曲网格可有效降低高阶方法的数值误差, 提高数值模拟精度. 本文在稀疏直网格的基础上, 首先对单元进行剖分生成六面体网格, 再通过插点升阶、投影保形、变形优化的步骤生成六面体占优高阶曲网格. 在生成过程中, 基于并发哈希表数据结构在直网格上添加高阶点, 物面高阶点采用多线程并行的方式投影到几何体, 同时采用基于R-Tree数据结构的局部化径向基函数方法对空间点变形, 以消除可能存在的负体积单元. 利用该方法对DLR-F6翼身组合体进行大规模高阶曲网格生成, 1655万单元采用16线程并行升阶到P2高阶网格耗时15.5 min, 并行效率达到54%. 最后, 通过GPU加速的PyFR高阶求解器进行数值模拟验证, 环形Couette流动精度测试结果显示在本文高阶网格上能够达到预期的精度阶. 此外, 圆球、椭球、SD7003机翼等3个不同雷诺数的典型算例结果证明本文生成的高阶曲网格能够满足高阶格式的计算需求.

     

    Abstract: Higher-order methods play a significant role in numerical simulations of turbulence, combustion, and aeroacoustics. When applied to higher-order methods, straight meshes may introduce non-physical solutions, whereas employing higher-order curved meshes can effectively reduce numerical errors and improve simulation accuracy. Based on initial coarse straight meshes, hexahedral-dominant(hex-dominant) higher-order curved meshes are generated by first subdividing elements into hex-dominant meshes, followed by order elevation via point insertion, geometry-preserving projection, and deformation optimization. During the mesh generation process, higher-order points are added to the straight mesh using a concurrent hash table data structure. High-order points on boundary surfaces are projected onto the geometry using a multi-threaded parallel approach. Additionally, a localized radial basis function method based on the R-Tree data structure is employed to deform interior points, untangling potential inverted elements. Large-scale higher-order curved mesh generation for the DLR-F6 wing-body configuration demonstrates that, starting from 16.55 million elements, elevating to P2-order curved meshes using 16 threads takes 15.5 minutes, achieving a parallel efficiency of 54%. Finally, numerical verification and validations using the GPU-accelerated PyFR higher-order solver are conducted. The accuracy test results for Taylor-Couette flow show that the expected order of accuracy is achieved on the high-order meshes presented in this paper. Other three validation cases—flow over a sphere, an ellipsoid, and a SD7003 wing—at different Reynolds numbers confirm that the generated higher-order curved meshes meet the computational requirements of high-order numerical schemes.

     

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