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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。
Grid technology is one of the key technologies in numerical simulation. Overlapped grids are a kind of grid technology that relaxes the topology requirements and reduces the difficulty of grid generation. Based on the structure overlapped grid, this paper researches and improves the methods of digging holes, finding points and optimizing the hole respectively. At the same time, it completes the overlap of object surfaces and forms a robust and automatic grid overlapping system. In the aspect of digging holes, combined with the method of “minimum hole mapping”, the method of “composite digging” is proposed to save the memory overhead. In the aspect of searching, the lattice space grid is constructed to ensure the continuity of search space, In combination with the idea of “effective search”, some grid points that do not contribute to the search are excluded, and then ADT tree nodes are reduced. On the aspect of optimization of the hole, the change discriminant rule is introduced and two kinds of protected points are introduced, Layer interpolation boundary is established to improve the robustness. On the object-surface grid overlap, the object surface projection method is used to complete the coordinate correction to realize the accurate transmission of the grid-flow variable near the object surface. In order to validate the proposed method, the numerical simulation of the flow-around and unsteady wing mounting and detachment of the steady wing combination DLR-F6 is carried out. The calculated results are in good agreement with the experimental results. The steady and unsteady disturbing flow has better numerical simulation ability and higher simulation accuracy, and has higher engineering application value.