非结构重叠网格显式装配算法

针对重叠网格中洞映射法占用过多物理内存的问题，发展了一种改进型洞映射法；基于相邻单元搜索法，发展了一种基于相邻阵面的贡献单元搜索法；通过将割补法与隐式切割技术相结合提出了一种非结构重叠网格显式装配算法。该算法首先生成一套包围物面的笛卡儿网格，其次存储所有与物面边界相交的笛卡儿网格信息，最后根据所存储笛卡儿网格与所需判断的网格单元的相对位置来判断其是否为洞内单元。在成功判断出所有洞内单元后，以当前洞边界为初始阵面推进，同时以各个网格单元的物面距离为判别标准对重叠区域进行优化，生成最终插值边界。所提算法优化了传统非结构重叠网格装配过程，具有物理内存占用低，贡献单元搜索次数少以及计算效率高等特点。通过2个典型复杂流动算例验证了所提算法的准确性与适用性。 

Explicit assembly algorithm of unstructured overset grid

To solve the problem that the hole mapping method occupies too much physical memory, an improved hole mapping method was developed. Based on the neighbor-to-neighbor search algorithm, a donor search method based on adjacent front was developed. An explicit assembly algorithm of unstructured overset grid was presented by combining the cut-paste method with the implicit cutting technique. First, the algorithm generated a set of Cartesian grids surrounding the wall surface. Second, those Cartesian cells intersecting the wall surface were stored. Finally, relative positions of the stored Cartesian cells were used to determine whether a grid point was inside the wall. After successfully determining all the grid points inside the wall, the current fringe grid points were used as the initial front, and the overlapping area was optimized by the wall distance of each grid point to generate the final interpolation boundary. The proposed explicit algorithm optimizes the traditional implicit assembly process of unstructured overset grid. It features in low physical memory occupation, low cost of donor searching and high computational efficiency. The accuracy and applicability of the proposed explicit method were verified by two typical complex flow examples.