Shock interactions in inviscid air and $$\hbox {CO}_2$$–$$\hbox {N}_2$$ flows in thermochemical non-equilibrium

Abstract

The present study aims at providing insights into shock wave interference patterns in gas flows when a mixture different than air is considered. High-energy non-equilibrium flows of air and $$\hbox {CO}_2$$ CO 2 –$$\hbox {N}_2$$ N 2 over a double-wedge geometry are studied numerically. The impact of freestream temperature on the non-equilibrium shock interaction patterns is investigated by simulating two different sets of freestream conditions. To this purpose, the SU2 solver has been extended to account for the conservation of chemical species as well as multiple energies and coupled to the Mutation++ library (Multicomponent Thermodynamic And Transport properties for IONized gases in C++) that provides all the necessary thermochemical properties of the mixture and chemical species. An analysis of the shock interference patterns is presented with respect to the existing taxonomy of interactions. A comparison between calorically perfect ideal gas and non-equilibrium simulations confirms that non-equilibrium effects greatly influence the shock interaction patterns. When thermochemical relaxation is considered, a type VI interaction is obtained for the $$\hbox {CO}_2$$ CO 2 -dominated flow, for both freestream temperatures of 300 K and 1000 K; for air, a type V six-shock interaction and a type VI interaction are obtained, respectively. We conclude that the increase in freestream temperature has a large impact on the shock interaction pattern of the air flow, whereas for the $$\hbox {CO}_2$$ CO 2 –$$\hbox {N}_2$$ N 2 flow the pattern does not change.

Impact of Anisotropic Mesh Adaptation on the Aerothermodynamics of Atmospheric Reentry

“…The use of the library ensures an appropriate closure of the governing equations for a wide range of temperatures and the use of multi-temperature models for non-equilibrium flows, with the aid of high-fidelity physical models. The coupling has been thoroughly validated [14]. The library has the ability to efficiently compute the thermodynamic, transport and chemical kinetic gas properties for any given custom mixture.…”

Influence of Thermochemical Modelling of CO2-N2 Mixtures on the Shock Interaction Patterns at Hypersonic Regimes

“…The solver is rapidly establishing itself within the open-source community as a prominent software for multiphysics analysis and design, including the simulation of chemically-reactive and nonequilibrium flows [27] with the development of SU2-NEMO (NonEquilibrium MOdels solver). Extensive validation of the software is reported in the literature [14,15]. The-closure-of the governing equations for the system that describes hypersonic flows is achieved by means of coupling with appropriate thermochemistry models (presented in Section II.A).…”

“…The library has been designed for robustness over a wide range of temperatures and its accuracy in dealing with multi-temperature models, with the following constraints in mind: 1) high fidelity of the physical models, ensuring that the laws of thermodynamics are satisfied and that results are validated against existing experimental data, 2) low computational cost, 3) a modern, object-oriented, extensible framework, and 4) detailed in-source and user's guide documentation in order to facilitate model improvement and collaboration. The library has been extensively validated as a software on its own [21] and some validation work has been carried out for the coupling of Mutation++ with the SU2-NEMO solver [14].…”

“…Morever, regions of thermal nonequilibrium were very small, due to the fast vibrational relaxation. Recent studies conducted by the authors of this paper [14] compared shock interaction patterns resulting from an inviscid Mach 9 flow over a double-wedge, for air and CO 2 mixtures. Numerical results lead to two important conclusions: 1) for lower freestream temperatures, the nonequilibrium shock interaction patterns differ between air and CO 2 flow, with a large impact on the surface pressure distribution, 2) a comparison with a perfect ideal gas model revealed that, despite the small degree thermal nonequilibrium encountered in the case of CO 2 , it still has a significant impact on the obtained interaction pattern and therefore vibrational excitation should be accounted for.…”

“…A CO 2 -N 2 mixture model is used to mimic the Martian atmosphere. Simulations are performed with the open-source CFD code SU2 [15], with the specific branch SU2-NEMO [14] dedicated to the study of hypersonic flows with high-temperature effects. The complexity of these type of flows typically results in regions of nearly-uniform flow properties separated by very localized and very high-gradient flow features such as shock waves, contact discontinuities and boundary layers.…”