Description: Design of reentry vehicles is driven by aeroheating concerns at elevated flow enthalpies. As such, accurate simulation of hypersonic flow phenomena such as detached bow shocks is of critical importance for reducing conservatism in design and unlocking improved performance. Adaptive mesh refinement (AMR) is an enabling technology to efficiently reduce numerical error in hypersonic reacting flow simulations by providing mesh resolution only where it is needed, based on flow phenomena or an engineering quantity of interest. ATA Engineering, Inc., proposes to develop, in collaboration with Mississippi State University, a toolset for Hypersonic Anisotropic Adaptive Mesh Refinement (HAAMR). HAAMR will offer anisotropic AMR, the efficiency of which improves as the square of anisotropy when compared to an isotropic approach. Furthermore, its metric-based adaptation will align the mesh faces to the underlying metric field. This approach will align the adapted mesh to a hypersonic bow shock, greatly reducing the numerical error associated with prediction of key figures of merit such as surface heat flux in unstructured grids. In addition to the HAAMR framework, the team will make improvements to the analysis workflow components. The metric-based anisotropic adaptation algorithms within the Advancing-Front/Local-Reconnection (AFLR) suite of meshing tools will be enhanced to enable higher-quality 3D grids, and robust numerical methods for gradient calculations will be implemented into the Loci/CHEM computational fluid dynamics (CFD) solver, enabling stable simulation on highly anisotropic adapted meshes. The team will leverage several decades of experience developing the underpinning CFD algorithms and AMR approaches. Phase I will conclude with a quantitative assessment of the value added by the envisioned toolset: comparisons of time to solution and accuracy for a reentry heatshield problem will be made using HAAMR, current AMR approaches, and legacy NASA tools.

Benefits: HAAMR will address a critical NASA bottleneck—mesh generation and adaption—across all atmospheric entry missions, such as high-speed crew return, high-mass Mars landers, and Venus and gas/ice giant probes. The unstructured AMR capability, targeted for hypersonic reacting flow solvers, will focus on the well-known spurious heat flux prediction problem intrinsic to steady-state simulation of hypersonic bow shocks, with modular design for future enhancements like unsteady flow.

Potential applications of HAAMR include improving the workflow for analysis and optimization of DoD and prime contractor hypersonic vehicles. The toolset could also prove useful to industry developing future supersonic and hypersonic commercial transport aircraft. Aside from hypersonics, any commercial CFD analysis could benefit from a more efficient mesh adaptation process.