Simulation of Graphite Ablation using an Overset Near Body Solver on an Adaptive Block-Structured Cartesian Off-Body Grid

The simulation of ablative environments provides a number of challenges for numerical methods such as accurate predictions of surface heating loads, shock tracking as the geometric shape changes, and the need to generate high-quality near-wall grids. For accurate heat flux predictions, the proposed solver in this work employs the CHAMPS Cartesian grid solver to simulate the flow around re-entry vehicles while adaptive mesh refinement is used for shock and wake structure tracking. This approach allows for highly automated simulations that only require the geometric surface triangulation as an input. However, the inability to use high aspect ratio cells to efficiently resolve boundary layer gradients has rendered Cartesian solvers infeasible for this application due to the large computational expense needed to fully resolve near-wall gradients. Therefore, the Cartesian solver used here has been coupled to a body-conformal near body solver such that the near-wall gradient is captured accurately and efficiently while maintaining the advantage of automatic grid generation. This new solver is validated for use in high-enthalpy flows and is able to accurately capture thermo-chemical non-equilibrium effects as well as surface heating loads. The proposed solver is then coupled to the KATS material response solver to simulate steady-state graphite ablation for a blunt cone on a ballistic re-entry into Earth. The coupling of the two solvers is fully parallelized and designed to be compatible with non-conformal grids at the geometry surface.