Numerical Study On Electron Density And Collision Of Sheath Of Hypersonic Vehicle

Formation of a plasma layer in high speed vehicle reentry is a complex phenomenon.As it encounters a dense atmosphere,a strong shock is formed in front of the air-spacecraft to heat the surrounding air-gas and to create a plasmasonic sheath.The kinetic energy of the gas is then converted into heat energy in the shock,and the air wrapped around the air-spacecraft goes through chemical reaction,vibration excitation,and ionization.The high temperature effect of the flow field in the plasmasonic sheath thus causes a series of problems,such as “blackout” and “thermal barrier”.The interaction between electromagnetic waves and the plasma then brings serious problems to air-spacecraft communication,remote sensing and cotrolling,GPS signals,and so on.As the source of the “blackout” problem,the plasmasonic sheath problems then become key issue in air-spacecraft reentry.It is necessary to predict the characteristics of the sheath to provide a reference for the “blackout” problem solution.The plasmasonic sheath of hypersonic flying vehicles is studied in this paper numerically.By considering the real gas conditions and thermochemical non-equilibrium conditions,the simulation method is established.Based on previous research progresses,the calculation was carried ou.Corresponding simulation codes were written based on USim softwares.The main work of this paper includes three aspects as follows:(1)Numerical simulation of thermochemical nonequilibrium flow field surrounding hypersonic vehiclesOn the basis of a commercial software USim,and considering the influence of chemical reaction dynamics on simulation results of he thermochemical non-equilibrium flow field,a two-dimensional axisymmetric blunt cone experimental model has been applied and analyzed by thermodynamic and chemical reaction kinetic models.According to the simulation results,characteristics of the plasmasonic sheath are analyzed in details,considering the influence of various flight heights on the temperature,shock wave distance,electron number density inside the sheath,and the collision between electrons and neutral particles.(2)Numerical simulation of thermochemical nonequilibrium flow field of hypersonic space vehicle under multi-component and multi-reactionOn the basis of the two-dimensional axisymmetric model considering the thermodynamic and kinetic effects of chemical reactions,the multi-component and multi-reaction numerical simulation model is established.Then,according to different flight conditions,the distribution cloud diagram of electron number density,electron and neutral particle collision is given,and the distribution rules of two important parameters at different flight heights and at different wall positions at the same flight height are analyzed according to different parameters such as temperature,pressure and flow rate.(3)Three-dimensional Numerical simulation of thermochemical nonequilibrium flow field of hypersonic space vehicle with Angle of attackBased on the two-dimensional model,a simple three-dimensional program is built,and the simulation cloud map is given through calculation.By analyzing and comparing the internal characteristics of sheath with or without Angle of attack.