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.