重叠网格中隐式装配策略的改进

作为重叠网格技术的重要组成部分，隐式装配没有显式的“挖洞”过程，仅需在搜索贡献单元的同时通过对比不同单元的品质来分类单元。通过对传统隐式装配过程进行改进，提出了一种更高效的隐式装配策略，减少了贡献单元的搜索次数；同时，提出了一种基于笛卡儿网格映射的局部贡献单元搜索法，提高了网格装配效率。首先，针对每一个子网格，在计算其到自身物面的最短物面距离的同时也计算到其他所有物面的最短物面距离；然后，通过比较同一单元到不同物面的最短物面距离来控制洞边界的位置；最后，仅对插值单元进行局部的贡献单元搜索，避免了针对所有单元进行全局贡献单元搜索的过程。通过3个典型复杂流动算例验证了所提方法的准确性与高效性。 

Enhancement of implicit assembly strategy in overlapping grids

As an important part of the overlapping grid technology, the implicit grid assembly has no explicit "hole-cutting" process, and it is only necessary to classify cells by comparing their qualities while searching for donor cells. By improving the traditional implicit assembly process, a more efficient implicit assembly strategy is developed to alleviate the effort of searching for donorcells. At the same time, a local donorcell search method based on Cartesian grid mapping is developed to improve grid assembly efficiency. First, for each sub-grid, the shortest distances to all other wall surfaces are calculated while calculating the shortest distance to its own wall surface.Then, the position of hole boundary is controlled by comparing the shortest distances of the same cell to different wall surfaces. Finally, only partial donorcell search is performed on interpolation cells, which avoids the process of global donor cell search for all cells. The accuracy and efficiency of the developed strategy are verified by three typical complex flow examples.