| The near-space hypersonic vehicle plays an important role in the development of national security in the future.It is a top technology that countries compete for and has developed rapidly in recent years.However,when the flying speed of the aircraft reaches a certain critical value,the kinetic energy of the aircraft will be converted into the internal energy of the surrounding air,resulting in a high temperature effect,leading to a series of complex chemical reactions and physics such as dissociation,ionization and atomic recombination of the air around the aircraft.Eventually a "plasma sheath" is generated around the aircraft.The existence of “sheaths” can cause a series of serious problems,such as influencing radar detection,communication between the aircraft and the ground.Based on the research status at home and abroad,this dissertation uses the simulation software to simulate the flow field around thermochemically non-equilibrium gas in a typical target hypersonic vehicle.The plasma temperature,pressure,and distribution of chemical components in the flow field around the flow are obtained.The influence of different factors on the simulation results is analyzed.In addition,a simulation study was conducted on the shock tube problem to introduce changes in the flow field in the shock tube under ideal conditions,this is the main innovation point of this article.The effect of different cross-section shapes on the flow field distribution in the shock tube was analyzed,and the formation mechanism of the oblique shock wave in the shock tube was discussed.A large amount of data is provided for subsequent plasma calculations.The main work of this dissertation is as follows:1.The theoretical knowledge of hypersonic thermochemical non-equilibrium simulations is introduced,such as thermodynamic equilibrium and non-equilibrium models,chemical equilibrium and non-equilibrium models,gas dissociation,ionization and recombination,etc.The basic theory of CFD is also introduced.Including flow control equations,thermochemical models,setting of solution conditions,etc.2.The RAMC-II flight experiment was simulated and the effects of different chemical reaction models on the simulation results were analyzed and compared with the references.The flow field simulation was performed on the three-dimensional dull cone model,and the effects of temperature model,height,Mach number,angle of attack and other parameters on the flow field simulation results are analyzed,especially the impact of angle of attack on simulation results is one of the innovation points in this dissertation;3.Study shock tube problems.Firstly,the qualitative description of the parameters of the flow field in the shock tube under ideal conditions is given,and the forward shock wave equation is deduced.Secondly,through the modeling,meshing and flow field simulation of shock tubes with different sections,the effect of section shape on the gas motion in the shock tube is analyzed;Finally,the Ф800mm shock tube was simulated to investigate the effect of the shock wave and the test section. |
