Numerical Simulation Of The Flow Field And Radiative Properties For Hypersonic Vehicle In High-temperature Environment

In recent years,hypersonic technology has set off a wave of domestic and foreign research,especially the radiative properties due to the heated air during the hypersonic vehicles reentry.It is well known that under the extremely high temperature,air will undergo a variety of complex physicochemical processes such as ionization dissociation and recombination which make it impossible to describe the radiation phenomenon using the classical gas dynamics.Some studies on equilibrium and non-equilibrium radiation caused by the heated air are carried out in this paper.We divided the ideas into two parts according to the research on the above-mentioned problems.Firstly,the Navier-Stokes equations should be solved to obtain the flow field parameters,after then,the spectral radiative properties can be modeled and calculated based on the parameters.Therefore,this paper consists of two main tasks:（1）Without regard to the surface catalytic effects,ablation effects and the influence of turbulence,we studied the equilibrium and thermochemical non-equilibrium flow field of the RMC-II flight using the CFD-FASTRAN software.This paper focuses on the simulation of flow field for RMC-II flight at different flight altitudes（61km,71km and81km）and the flow field parameters distribution on the stagnation line are obtained.Through the analysis of the calculation,the results show that whether in a thermochemical non-equilibrium flow field,the temperature of the gases rise sharply after the shock wave,and the vibration temperature of the thermochemical non-equilibrium flow field tends to lag behind the translational temperature.In the energy relaxation zone,the temperature drops until the equilibrium is restored near the wall.The more significant the non-equilibrium effect increases with height,the more the peak of the gas temperature and the shock standoff distance increase with the increase of the flying altitude.Within the range of error and accuracy,the results of this paper are in good agreement with the literature.（2）Based on the flow field parameters obtained by the above simulation,the equilibrium and the non-equilibrium radiation are simulated by selecting a point in the shock layer of the equilibrium and the thermochemical non-equilibrium flow field respectively.The radiation of RMC-II flight at three different altitudes was studied for the non-equilibrium flow field comparison and the influence of different temperature for the equilibrium radiation is investigated based on the obtained density of gas particles.Through the analysis of the calculation,the results show that for a single species,the radiation generated by different electron transitions is continuous spectrum and mostly in ultraviolet region,and its absorption and emission have obvious characteristics.The absorption and emission are almost one-to-one correspondence,that is,the characteristic wavelength absorption of strong emission is also strong.In general,the emission and absorption of each kind of gas band remain almost the same order of magnitude.The equilibrium radiation is greatly affected by temperature,and the higher the temperature,the stronger the radiation.In non-equilibrium radiation,absorption and emission are attenuated as the flight altitude increases.The radiation bands of different gases behave differently,and the radiation bands of different bands for the same kind of gas also differ.In general,the band with stronger radiation is about:5?10³¹.5?10⁴ cm^1-,2.5?10⁴³?10⁴ cm^1-and5?10⁴⁶?10⁴ cm^1-.