The NASA 2030 vision study identified automatic robust mesh generation from complex CAD geometry as a key bottleneck in CFD simulation. A common solution for dealing with CAD-related meshing failures is to perform some type of manual CAD clean-up prior to, or during meshing. This human intervention is an expensive bottleneck and is a serious obstacle in achieving large-scale automation. We present an alternative approach to automatic CAD clean-up that requires little change to the orginal CAD geometry and enables most surface mesh generators to "mesh over" unwanted CAD features, such as short lines, sliver faces, etc... The approach is based on grouping large numbers of CAD faces (usually tangential connected) in to "zones" which are then embedded in a curved trianglular mesh which captures the CAD surface curvature. The zones are then parameterised using a novel untangling technique that ensures (in vast majority of cases) a valid unfolded parameter space over large complex zones. Finally the large parameterised zones are meshed using a standard Delaunay meshing algortihm coupled with Jacobian correction. We present examples of high quality surface meshes produced on complex real-world CAD geometries that contain many of the common modelling features that often cause problems with today's mesh generators.
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