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A procedure is presented for efficient generation of high-quality unstructured grids suitable for viscous flow applications. The present procedure uses an iterative point creation and insertion scheme wherein points are created using either advancing-front type or advancing-normal type point placement. Advancing-normal point placement is used to generate high aspect ratio elements. Initially, the connectivity for these generated points is obtained by directly subdividing the element which contains them, without regard to quality. This connectivity is then improved by iteratively using local reconnection subject to a quality criterion. For two-dimensions, a min-max criterion is used and for three-dimensions, a Delaunay in-sphere criterion followed by a min-ma% type criterion is used. The overall procedure is applied repetitively until a complete field grid is generated with a desired point distribution. In two-dimensions, triangular elements in the viscous regions are optionally combined to form quadrilateral elements. Results are presented for a variety of two-dimen-& sional configurations. Preliminary results are also presented for extension of the present viscous grid generation methodology to three-dimensions. The results demonstrate that highquality unstructured grids suitable for inviscid or viscous flow applications can be generated about geometrically complex configurations.

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Procedures are presented for efficient generation of high-quality unstructured surface and volume grids. The overall procedure is based on the well-proven Advancing-Front/Local-Reconnection (AFLR) method. The AFLR triangular/tetrahedral grid generation procedure is a combination of automatic point creation, advancing type ideal point placement, and connectivity optimization schemes. A valid grid is maintained throughout the grid generation process. This provides a framework for implementing efficient local search operations using a simple data structure. It also provides a means for smoothly distributing the desired point spacing in the field using a point distribution function. This function is propagated through the field by interpolation from the boundary point spacing or by specified growth normal to the boundaries. Points are generated using either advancing-front type point placement for isotropic elements, advancing-point type point placement for isotropic right angle elements, or advancing-normal type point placement for high-aspect-ratio elements. The connectivity for new points is initially obtained by direct subdivision of the elements that contain them. Local-reconnection with a min-max type (minimize the maximum angle) type criterion is then used to optimize the connectivity. The overall procedure is applied repetitively until a complete field grid is obtained. An advancing-normal procedure is coupled with AFLR for anisotropic tetrahedral and pentahedral element grids. Advancing along prescribed normals from solid boundaries generates layers of anisotropic elements. The points are generated such that either pentahedral or tetrahedral elements with an implied connectivity can be directly recovered. The AFLR surface grid procedure uses an approximate physical space grid to define the surface during grid generation. The mapped space coordinates are mapped back to the actual surface at completion. Multiple surface definition patches are grouped into a single surface. A global mapping transCorrespondence and offprint requests to: formation is generated for the single surface using the grouped surface connectivity. The mapping coordinates are obtained by solving a coupled set of Laplacian equations. The overall procedure has been applied to a wide variety of configurations. Selected results are presented which demonstrate that high-quality unstructured grids can be efficiently and consistently generated for complex configurations.