| In this thesis,the "black barrier" characteristics of the reentry vehicle and the factors affecting the signal communication efficiency are studied,the flow field characteristics around the reentry vehicle are simulated,and the transmission characteristics of terahertz waves in plasma flow field under different conditions are numerically calculated:(1)The physical significance and engineering value of the study of "black barriers" is explained,and the need for this research and the limitations of the current progress are discussed with examples of domestic and international research results in this area.In this paper,the physical simulation is used to obtain the parametric characteristics of the "black barrier",and this parameter is used instead of assuming mathematical model data to build the physical model of the "black barrier".(2)The re-entry flow field model is built based on N-S and thermochemical nonequilibrium equation.The non-magnetized plasma properties of black barrier with flow field characteristics are analyzed.The characteristics of terahertz wave and the reason of choosing Terahertz wave as carrier wave are analyzed by using electromagnetic wave transmission theory.(3)Based on the Park C chemical reaction model,the flow field characteristics around the RAM-C Ⅱ blunt reentry vehicle were solved.Using the earth atmosphere model of troposphere and stratosphere,the distribution characteristics of temperature,pressure and electron density in the flow field around the aircraft under different flow velocity and atmospheric characteristics are studied.At the same time,the physical mechanism of transforming air flow field into plasma flow field is explained,and the parameters of plasma flow field are analyzed.(4)Based on the simulation results,the scattering matrix method(SMM)is used to investigate the transmission characteristics of terahertz waves in the black barrier.The influence of different aircraft conditions on the transmission characteristics is discussed,and the influence of terahertz wave transmission characteristics is analyzed.In addition,the signal receiving terminal with external permanent magnet is modeled,and the gain effect of magnetic field is studied.The effects of permanent magnets with different magnetization characteristics on the transmission characteristics of terahertz waves are compared.The research shows that the temperature reflow field is mainly affected by the speed of the aircraft,the pressure is mainly affected by the flight altitude,and both of these factors have an impact on the electron density.The results show that the transmission characteristics of terahertz waves in plasma are mainly affected by electron density.In addition,the left-polarized THz wave,which is vertically incident,and the magnetic field applied at the receiving end will improve the communication ability of the carrier signal.These work provide data support and theoretical reference for the application of terahertz technology in "black barrier". |
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