Vibration Excitation of Hypersonic CO2 Rarefied Gas and Realization of DSMC Method

Abstract

In view of the unique CO2 rarefied gas environment of Mars and the high-temperature real gas effect during the high supersonic velocity entry of the rover into Mars,the excitation characteristics of CO2 multi-vibrational modes was studied. Unstructured grid and direct simulation Monte Carlo method (DSMC) and the non-resonant oscillator vibration excitation model was adopted in this paper. The dissociation energy of CO2was evenly divided into four vibration modes,and then the highest vibration energy level of each mode was limited,and a high temperature rarefied real gas chemical reaction model with 5 components 17 reaction containing CO2 was simulated. The high-temperature chemical non-equilibrium effect flow field of “Mars Pathfinder” was calculated at an altitude of 65 km with entry velocity of 7 453 m / s and angle of attack of 0° in the Martian atmosphere. The results show that the CO2 is decomposed dramaticlly after the excitation and consumes a large amount of energy. The percentage of components in the windward excitation and the properties of the probe surface are consistent with the literature results, which proves the feasibility of this paper for the CO2 vibration excitation treatment method. On this basis, the N2 component was added to simulate the flow field of the 8 component, 44 reaction of the Martian atmosphere, and the change of flow field characteristics was analyzed by changing the incoming flow density and Mach number. The results show that the flow field temperature increases and then decreases as the incoming flow density decreases,and the surface heat flow density increases. With the increasement of incoming Mach number, the flow field temperature and pressure increases,and the surface heat flow density increases. However,the Mach number shows little effect on the coetlicient of heat flow density.