Atmospheric reentry modelling using an open source DSMC code

Aerothermodynamic investigations of hypersonic re-entry vehicles provides crucial information to other key disciplines as structures and materials, assisting the development of efficient and lightweight thermal protection systems (TPS). Under the transitional flow regime, where chemical and thermal nonequilibrium are predominant, the most successful numerical method for such studies has been the direct simulation Monte Carlo (DSMC) numerical technique. In the present work, the solver dsmcFoam has been benchmarked against experimental, numerical, and theoretical data found in the open literature for inert and chemically reactive flows. The Quantum-Kinetic (QK) chemistry model with a full set of 19 chemical reactions has been implemented into the code and it proved to be essential in the correct prediction of the shock wave structure and heating flux to the vehicle’s surface during the re-entry phase. Having implemented the QK chemistry model, the dsmcF oam solver was employed to investigate thermal protection system discontinuities. These TPS discontinuities, representative of panel-to-panel joints or the impact of micro meteorites/ice droplets, were modelled as a family of cavities with different length-to-depth ratios. The results showed that the cavity length has a significant impact on the flowfield structure and aerodynamic surface quantities distribution inside and around the cavities. In addition, for L/D = 5, the flow separates at the cavity upstream lip and attaches to the cavity bottom surface, representing a potentially catastrophic feature under rarefied gas conditions. Furthermore, the same phenomena is only observed in the continuum regime when L/D > 14