Thermochemical Models for Hypersonic Regime

In the last decades, human’s ability to penetrate further into space and accomplish more complex missions has improved dramatically. In parallel, increasingly sophisticated and faster weapons, such as hypersonic missiles, have been developed. For these reasons, also the need to study the phenomena that occur while travelling at very high speeds has arisen in both the civil and military sectors. Hypersonic flows are significantly more challenging to simulate than conventional subsonic or supersonic flows, due to additional complex physical processes such as shocks, chemical reactions and plasma formation. Consequently, it is not possible to adopt the same numerical models and methods commonly used to predict the property and behaviour of low-speed flow, because they are incomplete and can not manage properly all the complexities that occur in hypersonic flow. First of all, a MATLAB code has been developed. It contains thermochemical atmospheres models of the Earth, Mars and Jupiter. Each model takes into account different chemical species and reactions. Therefore, the re-entry or landing of a capsule or any other spacecraft can be simulated in different scenarios. The software can calculate the equilibrium composition of a mixture and the thermochemical relaxation downstream a normal shock wave. The results obtained have been compared with data available in literature and the code has been validated. In second instance, the thermochemistry has been studied and implemented in a commercial code, specifically, STAR CCM+ by Siemens. One-dimensional CFD simulations have been carried out in order to study equilibrium conditions. Every analysis has been carried out by adopting a suitable physical model, numeric discretization scheme and fine enough grids to avoid numerical instabilities and to guarantee accurate results. The results of CFD analysis and MATLAB code are in line with each other, only slight differences have been detected. The results produced by the MATLAB code have been compared with those found in the literature. The chemical and energy transient calculations have been validated.