Numerical Simulation Of Magnetohydrodynamics Of Cylindrical Implosion Magnetic Compression Process

The cylindrical implosion magnetic flux compression generator(hereinafter referred to as the MC-1 generator)is a kind of high energy density loading technology,which uses explosive detonation to drive a metallic liner,compresses the internal preset magnetic flux to the vicinity of the axis to obtain an ultra-strong magnetic field,and produces a magnetic pressure on the metal sample.In this paper,a two-dimensional magneto-hydrodynamics code(named TriAngels-MHD)was used to simulate the working process of MC-1 generator.First,the pressure disturbance exerted on the outer surface of the liner is studied together with the viscosity and strength of liner material.The results show that the viscosity of the material has sizable effects on the development of perturbation at the inner interface of the liner.With a vanishing material viscosity,the perturbation tends to be perfectly smoothed.In order to obtain a most similar liner shape evolution as that of the experiment,the average viscosity of material(stainless steel 304)should set to be?0.6m2/s under the pressure-temperature conditions of the experiment.The influence of the material strength on the motion of the liner in the r-? plane can be ignored.Second,the Magneto-Rayleigh-Taylor(MRT)instability development at the liner's inner interface is studied.In the simulation case with an specific condition(i.e.,resistivity is zero and initial magnetic field is 10T),the perturbation at the inner interface of the liner forms the obvious MRT instability growth in the turning age,with an average growth rate of about 0.9134?s-1.While the resistivity of the material is taken into account,there is no obvious MRT instability growth.Finally,the magnetic flux compression ability was studied.In the case of ideal resistivity,the smaller the initial magnetic field is,the lower the conversion efficiency will be.The affection of the small pressure disturbance exerted on the outer surface on the magnetic flux compression capacity of the MC-1 generator is negligible.The magnetic diffusion process in the MC-1 generator was analyzed in detail by using a one-dimensional magneto hydrodynamics program--MC11D.The calculation results show that when the cavity magnetic field exceeds the critical magnetic field,which is determined by the liner material,the cavity magnetic field will diffuse rapidly into the liner in the form of a sharp-front magnetic diffusion wave.And the wave-front height of the steady propagating magnetic diffusion wave is kept around the material's critical magnetic field.In the magnetic compression process,the sharp-front magnetic diffusion wave and the plasma layer at the inner wall of the liner formed due to high temperature,have the opposite effects on the magnetic diffusion process.They compete with each other in the process,and take turns to play a leading role at different stages.An equation of state(EOS)in analytical form was introduced into MC11D to extend its application ability.The parameter in the equation of state was fitted according to the copper material,with a relative error less than 2%.The simulation results with the analytical EOS were consistent with the results using standard parameters and tabular equation of state equation,all are in good agreement with the experimental data.Using this improved,the MC11Dcode can now simulate materials not included in the tabular equation of state database.It provides a method for the analysis of experimental results and data processing.