Numerical Study On Thermo-chemical Nonequilibrium Flow With Magnetic Interference

At present,the major countries in the world attach great importance to the research of hypersonic flight technology.The aerodynamic heat problem encountered in the process of atmospheric reentry near space has been an serious problem to be solved.A solenoid magnet can be placed inside the blunt body imposing a magnetic field to control the conductive ionized air.The Lorentz force acts on the induced current to increase the standoff distance of the bow shock wave in order to achieve the purpose of heat mitigation.Meanwhile,the ionized air will give the solenoid magnet a reaction resistance reducing the speed of the vehicle indirectly alleviating aerodynamic heat.Based on the existing numerical simulation methods of magnetic fluid involving magnetic control thermal protection and magnetic control resistance increase,this paper studies numerical simulation methods of induced magnetic fields in the flow field under magnetic control and explores the influence of the induced magnetic field on the magnetic control system.Different form of MHD equations are derived for different simplifying assumptions.The numerical methods of the ideal MHD equations are implemented by the finite volume method in the AUSM+ scheme under the OpenFOAM framework.Several one-dimensional and two-dimensional classic cases are verified correctly.The governing equations of multi-species thermo-chemical nonequilibrium gases are established and the calculation of related coefficients are introduced.Numerical simulations of RAM-C II reentry capsule experiment under the conditions of Mach 23.9and Mach 25.9 are conducted to explore the differences between 7-species and 11-species chemical reaction model.It is found that the result by the 11-species chemical reaction model achieves a higher degree of ionization.Aiming at the numerical simulation of the magnetic control system of hypersonic vehicle,the heat reduction performance and resistance increase effect of the hemispherical cylinder are simulated based on the low magnetic-Reynolds number assumption.Decomposed MHD equations,a source-term approach based on magnetic induction equations and and a magnetic-correction approach based on magnetic vector potentials are introduced.The three methods are compared from theoretical and numerical results.It is found that the result of the approach based on magnetic vector potentials is more reliable with higher accuracy and robustness.Uncertainties in the computation of electrical conductivity of high temperature air are analyzed.Based on the uniform conductivity assumption,the effect of induced magnetic fields on the performance of the magnetic control system at different magnetic Reynolds numbers is explored.It is found that induced magnetic fields would reduce the shock standoff distance,and enhance the heat reduction effect and resistance increase characteristics of the magnetic control system.At a high magnetic Reynolds number,the enhancement effect is more obvious.