Numerical Study Of Unsteady Plasma Jets

In order to discuss the flow regularity of plasma jet in atmosphere,many scholars implemented the relative extensive theoretical,experiment and numerical calculation researches.Because of being limited by many conditions such as experiment cycles,experiment environment and economic factors,people always research this filed with the method of numerical simulation.With the development of computational fluid mechanics,research on the development process of plasma jet with numerical simulation computation has become the economic and effective means gradually.After the launch of the new concept weapons including electromagnetic railgun and electrothermal chemical gun,the unsteady and high-speed plasma jet will be erupted,which will harm the surrounding environment or equipment,such as electromagnetic radiation and high temperature ablation.Therefore,from the perspective of launch safety,the research on unsteady plasma jet is of great practical significance.With or without magnetic field,and under different initial conditions such as velocity and pressure distribution of unsteady plasma jet,the numerical simulation is implemented for the plasma jet flow field structure and its development process in this paper.Moreover,the development characteristics and deflection characteristics of plasma jet flow field are discussed.The numerical simulation on it is carried out with high-order computational scheme,comparing the flow field structure of unsteady jet under computational formats.In numerical simulation,the basic equations of two-dimensional part are the Euler equations without regard to viscidity,adopting Roe format and WENO format;the basic equations of three-dimensional part are Navier-Stokes equations,and MHD equation is solved,adopting AUSM equation for computing.The computation part of two-dimensional unsteady jet flow adopts second order Roe format,fifth order,seventh order WENO format respectively to compute shock tube Riemann problem,and selects fifth order WENO format to compute plasma under expanded jet.Comparing with the computed results of AUSM format,it can be seen that the dissipation of WENO format is small,and it can express the structural characteristics for showing under expanded jet.For the part of three-dimensional unsteady jet flow,the numerical simulation is mainly carried out for the deflection characteristic of plasma jet under magnetic field intensity and different initial conditions.The numerical results show that there is deflection for plasma jet under the action of magnetic field,and its angle of deflection increases with the increase of strength of applied magnetic field,presenting approximately linear change;different initial velocities and pressures will also affect the deflection of plasma jet,and the angle of deflection increases with the increase of velocity and pressure.