鲁棒的结构网格自动化重叠方法

网格技术是目前数值模拟中的关键技术之一。重叠网格是一种放宽拓扑要求、减小网格生成难度的网格技术。本文以结构重叠网格为基础，分别针对挖洞、寻点以及洞面优化方法进行了研究和改进，同时完成物面网格重叠，形成了一套鲁棒的、自动化的网格重叠系统。在挖洞方面，结合“最小洞映射”方法，提出“复合式挖洞”方法，节省内存开销；在寻点方面，通过构建格心虚网格，保证搜索空间的连续性，同时结合“有效搜索”思想，排除部分对寻点无贡献的网格点，进而减少ADT叉树节点；在洞面优化上，改变填补判别法则并引入两类受保护洞内点，确保两层插值边界建立，提高鲁棒性；在物面网格重叠上，利用物面投影法完成坐标修正，实现物面附近网格流动变量的准确传递。为验证本文方法，分别对定常翼身组合体DLR-F6绕流和非定常机翼挂载分离过程进行了数值模拟，计算结果与实验结果吻合良好，表明该结构重叠网格系统对多物体间定常、非定常扰流具有较好的数值模拟能力和较高的模拟精度，具有较高的工程应用价值。

A robust and automatic structured overlapping grid approach

The grid technology is a crucial aspect of numerical simulation up till the present moment. Overlapping grid technology could relax the restriction of structure topology, thus reducing the difficulty of grid generation. Based on the structured overlapping grid, hole-cutting, donor search, and overlapping optimization are explored and improved, and surface grid assemblage is completed in this thesis. Simultaneously, a robust and automatic grid overlapping system is constructed. In order to save memory, based on the minimum hole mapping method, a composite hole-cutting method is proposed. Regarding donor search, the continuity of the search space is preserved with the virtual cell-centered grid. Moreover, the nodes of alternating digital tree (ADT) are decreased by an efficient search algorithm which excludes some non-contributing grid points. With respect to overlapping optimization, two kinds of protected hole-points are inserted and a new principle is developed to ensure the construction of two interpolated layers in paste phase, intensifying the robustness of overlapping optimization. The coordinates of near-body grids are corrected by projection method to make sure the accurate transmission of flow variables. With the enhanced algorithm, a steady DLR-F6 wing-body flow and an unsteady wing/pylon/store separation flow are performed, and excellent agreement of computational results compared with experimental data has been achieved. The algorithm shows remarkable capability and accuracy in the simulation of steady or unsteady multiple bodies flow and provides great application value for engineering.