A fully automated Chimera methodology has been developed in this study to provide geometric or stencil information required to facilitate intergrid data communications. Chimera-holes are cut automatically in each grid of an overset grid system based on whether the grid overlaps with Non-Penetrable Surfaces (NFS) and/or blocked regions. The efficiency of the holecutting algorithm is boosted with search algorithms based on the state-of-the-art Alternating Digital Tree (ADT) data structures. The automatic hole-cutting algorithm has been used to produce data for both the conservative and the traditional Chimera methods. The automated nature of the hole-cutting algorithm is ideally suited for handling multiple moving body problems. Several cases, both steady and unsteady, are used to demonstrate the effectiveness of the methodology.

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A 2 n tree (capable of supporting binary, Quadtree and Octree) based viscous Cartesian grid generation method has been successfully developed for complex geometries. Compared with an Octree data structure, the 2 n tree data structure supports anisotropic grid adaptations in any of the coordinate directions in an arbitrary manner. This capability enables high resolution of flow features such as shocks, shear layers and wakes with high aspect ratio cells. In order to properly resolve viscous boundary layers, a viscous layer grid is "inserted" between the Cartesian grid and the body surface through a projection technique. The thickness of the viscous layer grid can be determined based on the expected boundary layer thickness. Algorithms to automatically detect and resolve narrow gaps, and geometrically critical features have been developed. The method completely avoids cell-cutting, and produces overall good quality computational grids. Several demonstration cases are included to showcase the capability of the method.