Construction of Hexahedral Block Topology and its Decomposition to Generate Initial Tetrahedral Grids for Aerodynamic Applications

Making an initial tetrahedral grid for complex geometry can be a tedious and time consuming task. This paper describes a novel procedure for generation of starting tetrahedral cells using hexahedral block topology. Hexahedral blocks are arranged around an aerodynamic body to form a flow domain. Each of the hexahedral blocks is then decomposed into six tetrahedral elements to obtain an initial tetrahedral grid around the same aerodynamic body. This resulted in an algorithm that enables users to produce starting tetrahedral grids for variety of aerodynamic bodies. To construct an initial starting tetrahedral grid suitable for computational flow simulations, representing a solid surface geometry (fuselage or a wing section) attached to a plane-of-symmetry, a topology containing at least 5 hexahedral blocks is required. The resulting initial starting grid consists of 30 tetrahedral cells with 74 faces and 16 vertices, which is the same number of vertices as for the hexahedral blocks. A face-based global data structure is then produced for the tetrahedral cells. To represent multiple surface definitions a topology containing nine hexahedral blocks is required. When decomposed, the nine hexahedral blocks, produce a tetrahedral grid consisting of 54 cells and 24 vertices.