Using quilts and chains to improve structured and unstructured surface grids

Many of today's organizations design and define their products in solid-model-based computer-aided design (CAD) systems. Analysis of these models via computational fluid dynamics (CFD) requires that the grid generator work with the boundary representation that the CAD system automatically produces. Unfortunately, the exact form of the boundary representation is closely linked to the solid model construction process, and is often divorced from the aerodynamic intent of the object. Described herein is a logical extension to traditional boundary representations, called quilts and chains, which gives the analyst the ability to work with the underlying solid model from the perspective of the aerodynamicist, instead of from the perspective of the CAD model builder. For analysts using unstructured grids, the consequence is that the unusually small triangles associated with the sliver faces that result from intersections, fillets, rounds, and other modeling idiosyncrasies will not be produced, thereby improving both the quality and grid-generation speed for many configurations. For analysts using structured grids, the consequence is that the grid can follow the aerodynamic intent of the body rather than the myriad of edges generated during the generation of the solid model; once again, improved grid quality and significantly decreased grid generation time result.