A Shock Fitting Technique For Hypersonic Flows Using Hexahedral Meshes
Flow feature-aligned mesh generation is a much-sought tool, especially for high Mach flows like hypersonic flows with strong shocks. Previous studies have shown that shock-fitted grids dramatically improve hard-to-predict variables such as heat flux. However, aligning the grid cells to shocks is a challenge both for structured and unstructured meshes. To address this challenge, a new feature in the structured multi-block meshing software, GridPro, has been developed. It facilitates shock-fitted grid generation by aligning the blocks in line with the shock contour. A Mach contour sheet extracted during post-processing of the initial flow field on the base grid is taken as a reference to re-align the blocks in line with the contour of the shock. The blocks in the vicinity of the shock are split and projected on the guiding surface. The split blocks align themselves orthogonal to the shock curvature at every point. In a couple of such shock-fitting iterations, the final blocking arrangement is arrived at. With the addition of just a few blocks, accurate and crisper capturing of the shock is achieved without an over-shoot in cell count. This process negates the need for multiple simulation-postprocessing loops as required in the adaptive meshing-based shock-capturing approach. This new technique is effective on complex geometries with multiple shocks. Efforts are underway to broaden the applicability of the technique to include wakes, shear layers, etc.