磁驱动飞片的一维磁流体动力学数值研究

磁驱动高速飞片技术是近年来发展的一种新型实验技术,在冲击波物理领域得到应用。该过程伴随着磁场扩散,并由此引起焦耳加热,使得飞片加载面的相状态发生变化,这决定了飞片厚度的范围。基于拉格朗日坐标系,利用磁流体动力学方程组、电阻率方程和状态方程数据库,对磁驱动铝飞片进行了一维磁流体动力学数值计算,获得了不同时刻铝飞片密度、温度的剖面分布,得到了磁场扩散速率随加载电流密度的变化关系。文章所选取的电导率方程只考虑到汽化点为止,对于等离子体形成的过程无法描述,如果要精确描述更高电流密度下的驱动过程,需考虑更为普适的电导率方程。磁场扩散速率随加载电流密度的变化存在转折点,在转折点前后可分别用两个线性关系表达式加以刻画。利用这些关系和冲击波物理相关知识,对磁压加载等熵驱动飞片实验样品厚度的选择进行了研究。

One dimensional magneto-hydrodynamic simulation of magnetically driven flyer plates

The technique of magnetically driven flyer plates is a new one developed for experiments in recent years,and it is applied in the field of shock wave physics.The process is accompanied by magnetic diffusion which causes the Joule heating,and the phase states of the flyer near the loading surface varied which determined the range of the thickness of the flyer.Based on the Lagrangian coordinates,one dimensional magneto-hydrodynamic simulation of magnetically driven flyer plates is done with the equations of magneto-hydrodynamics,equation of electrical resistivity and database of equation of states(EOS).The distributions of density and temperature of Aluminum flyer along Lagrangian coordinates for different times are obtained,and the relationship of magnetic diffusion velocity varying with loading current densities is gained.For the equation of the electrical resistivity chosen here,it can only describe the state of the flyer before vaporization points and can not describe the subsequent process such as plasma forming,which needs universal equation of electrical resistivity.A turning point appears during the process of magnetic diffusion velocity varying with the loading current densities,and the relationships can be expressed with two linear equations before and after the turning point.According to the results above and knowledge of shock wave physics,the choice of the thickness of magnetically driven flyer plates is studied.