Hybrid prismatic/tetrahedral grid generation for complex 3-D geometries

An algorithm for the generation of hybrid prismatic/tetrahedral grids for complex 3-D geometries is presented. The method marches a triangulated surface grid away from the body to form a semi-unstructured prismatic grid. The outermost layer of this grid is then used in an octree refinement scheme to produce a tetrahedral grid. The tetrahedra are linked directly to the nodes of the outermost prismatic layer. The resulting hybrid grid is suitable for performing Navier-Stokes calculations in the viscous region (prismatic grid) near the body and Euler calculations in the inviscid region (tetrahedral grid) away from the body. The hybrid grid approach provides considerable flexibility in generating meshes around complex 3-D geometries. Other advantages of the developed grid generator are its speed, simplicity, direct control of grid orthogonality and spacing, as well as its generality for treatment of 3-D geometries. An F-16A aircraft was considered in the applications in order to investigate efficiency and to demonstrate robustness of the method in handling relatively complex topologies. Grid generation time for the entire aircraft domain was less than 10 minutes on a Sun workstation running at 2 mflops.