TEMPLATE-BASED HEXAHEDRAL MESH GENERATION FOR TURBINE COOLING GEOMETRIES

This paper describes a multiblock grid generation method for turbine cooling geometries. The method is based on the observation that cooling films are essentially branches inserted on a large trunk, represented by the passage or by the cooling duct. The small size of the films compared to the overall size of turbine blades allows simplifications to be introduced with respect to general-purpose trunk and branch algorithms. The grid generation starts from an existing layout for the passage or cooling duct grid and operates on a Cartesian patch of the trunk surface. The patch is hollowed and a templated branch layout is inserted. Padding blocks are created to connect the two layouts into a single, boundary conforming layout. The resulting multiblock grid is then smoothed using a modification of Thompson's Poisson system. The boundary mesh distribution is not prescribed. Instead, boundary orthogonality is enforced and elliptic smoothing is performed on the boundaries as well as inside the volume. The grid size control relies on a novel Newton-like update for the control functions of the Poisson system. The smoothing step is essential in achieving good grid quality throughout and determines, in part, the template for a given configuration. The algorithm is particularly suitable for large arrays of films or other cooling decoration and results show that the proposed method can produce grids of better quality than existing methods.