Fully-Coupled Simulation of Low Temperature Ablator and Hypersonic Flow Solver

Interaction between physical systems in nature occur seamlessly, where two or more processes affect each other and proceed to an equilibrium. Modeling physical processes using numerical tools however, requires to force the interaction between the two models at certain discrete times to obtain accurate solutions. In this study a one-dimensional transient material thermal response solver with surface ablation is developed and coupled to a hypersonic flow solver. The development of the interaction simulation proceeds with detailed explanation of the fluid and material response solvers. The complex interaction between the two physics is modeled with internal convergence sub-loops that converge the state variables at each simulation time step. The developed ablation scheme in the material response solver is verified using the so-called Q-star approach, showing excellent agreement. The solver is then coupled to the Cartesian Higher-order Adaptive Multi-Physics Solver (CHAMPS). CHAMPS utilizes a higher-order adaptive block-structured Cartesian grid for resolving the off-body flow-field and internally couples to a body-conformal near body solver (NBS) grid for capturing the boundary layer. The combination of these two flow solvers allows for the hybrid approach to accurately and efficiently predict surface heating loads in hypersonic viscous flows for any arbitrarily complex geometry without the need for manual grid meshing or complicated mesh motion algorithms. The fluid ablation interaction (FAI) solver used here tightly couples the CHAMPS fluid solver and 1D material response solver by exchanging a full set of boundary conditions at shared interface. The flow simulation is advanced in time using an unsteady implicit scheme with dual time stepping to allow for relatively large time steps to be taken. The FAI solver is validated for a Mach 6 flow over a two-dimensional, axisymmetric sub-scale Phoebus capsule geometry covered by a layer of camphor material with a copper sub-structure. The material geometry is discretized using an array of material response solvers with varying types of elements. The effect of the coupling frequency between the solvers as well as effect of transport properties is explored and results obtained with the FAI solver are presented and discussed.