A folding/unfolding algorithm for the construction of semi-structured layers in hybrid grid generation

A method is presented for generating semi-structured layers in hybrid grids suitable for high Reynolds number flow simulations. It can produce superior quality grids around convex and concave ridges of the domain compared to a standard prismatic or advancing layers generator. In a first step, hybrid quadrilateral/triangular grids are employed to cluster the surface grid towards sharp corners and ridges. Starting from this surface grid as an initial front for the volume grid generation, a prismatic and hexahedral layers generation technique is used, containing degenerate faces to add or remove elements in convex or concave areas of the geometry respectively. The method can automatically create structured-like grids in concave gaps and better discretize the space around convex ridges to improve overall accuracy. The final grid remains conforming to not complicate the solver and post-processing requirements. Several examples illustrate the application of the method.