High-fidelity simulation of ablating materials subjected to high-enthalpy flows
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The atmospheric re-entry of spacecraft involves high heat load and a wide range of complex physico-chemical phenomena. To design thermal protection systems, numerical tools capable of accurately modeling these phenomena are required. In this contribution, a staggered coupling strategy between a flow solver and a material solver is proposed to overcome the limitations of standalone solvers. This approach enables the consideration of complex multi-physics interactions while avoiding the high computational cost associated with a fully unified solver [Schrooyen2017]. The flow solver, ArgoDG [Hillewaert2013], computes the high-enthalpy aerothermal environment and benefits from high-order accuracy through the use of the discontinuous Galerkin method. The material solver, PATO [Lachaud2014], models the thermal and mechanical responses of the ablative material, including heat transfer and pyrolysis processes. Ablation and the resulting deformation of the solid shape are tracked using a moving mesh on the material side and an immersed interface method on the flow solver side, to avoid the complexity and computational cost of remeshing a deforming interface. A comprehensive set of boundary conditions is implemented on both solvers to account for complex surface chemistry processes such as ablation, catalysis, and pyrolysis. Since the surface chemistry may lead to stiff numerical problems, particular effort has been devoted to ensuring a robust implementation of these boundary conditions along the immersed interface. Thus, the fluxes are implicitly imposed within the implicit time marching approach of the flow solver, instead of recalculating the mass and heat balances to adapt them to the fluxes, as is usually done in the literature. The coupling relies on the preCICE library [Chourdakis2022] to manage data exchange between the solvers, including mapping and interpolation at the interface. Experiments obtained in the Plasmatron facility of the von Karman Institute (VKI) [Turchi2019, Helber2016] are reproduced numerically to validate both the coupling strategy and the underlying physical models.
