In this paper, we analyze the modification of fast particles on the nonlinear radial displacement of m = 1 internal kink mode with a shoulderlike equilibrium current theoretically. Using the matching method on the solutions of the outer and inner regions, we derive the analytical form of nonlinear radial displacement in the limit of q' = q" = 0, which is valid to the cases of weak shear due to a slight flattening of the q(r) profile around q = 1. We have taken into consideration the effects of the circulating and trapped fast particles on the nonlinear state of the mode. It is found that a fast particle can modify the nonlinear saturation level by the change of potential energy, depending on the fast particle properties. By the matching of linear dispersion relation to early nonlinear result, we also obtain the relations of radial displacement to the mode frequency and linear growth rate, and discuss the scaling for different stabilities of the MHD modes.

The interaction between a converging cylindrical shock and double density interfaces in the presence of a saddle magnetic field is numerically investigated within the framework of ideal magnetohydrodynamics. Three fluids of differing densities are initially separated by the two perturbed cylindrical interfaces. The initial incident converging shock is generated from a Riemann problem upstream of the first interface. The effect of the magnetic field on the instabilities is studied through varying the field strength. It shows that the Richtmyer-Meshkov and Rayleigh-Taylor instabilities are mitigated by the field, however, the extent of the suppression varies on the interface which leads to nonaxisymmetric growth of the perturbations. The degree of asymmetry of the interfacial growth rate is increased when the seed field strength is increased.

提出了一个弛豫磁流体力学模型,特别适合电磁驱动真空-等离子体系统的数值模拟.该模型和Seyler采用的弛豫模型有相似之处,即采用全电磁模型,不同的是采用忽略电子惯性项的广义欧姆定律直接作为本构来封闭麦克斯韦方程,减少了独立变量,是适合此类问题的最简模型.分析了磁流体力学模型电磁部分的色散关系,从而论证了其在真空区退化为电磁传播,在等离子体物质区退化为磁扩散近似,并且相速和群速是有上界的.改进了Seyler采用的时间离散方式,从而将时间精度从1阶提高到3阶,时间步长不受刚性源项约束,只受系统最大的特征速度确定的柯朗-弗里德里奇-列维(CFL)条件约束,便于显式计算和大规模并行化.

采用FOI-PERFECT程序对局域欧姆加热主导的动态烧蚀进行了数值模拟研究,定量诊断并比较了烧蚀率、先驱电流和烧蚀时间,考查烧蚀阶段之初的丝等离子体的直径和丝阵的丝数对烧蚀的影响,结果表明,在等离子体流建立后,随丝数或者丝径的增加,烧蚀率增大,先驱电流减少,烧蚀时间减小。

反场构形(FRC)预加热磁化等离子体是磁化靶聚变(MTF)中等离子体靶的主要形成方法之一。为了从物理机理及物理本质上更好地理解反场构形磁化等离子体的平衡状态, 依据FRC等离子体的经典刚性转子(RR)模型, 通过对平衡状态的解析求解, 获得了等离子体各主要参数在平衡状态下的分布函数, 并与标准二维磁流体力学(MHD)的数值模拟结果进行对比分析, 在此基础上讨论了RR模型参数对平衡状态分布函数的影响。结果表明, 在FRC等离子体分界线内部, RR解析模型可以较好地描述等离子体状态分布。

丝阵烧蚀在丝阵Z箍缩动力学中扮有重要角色, 透彻理解丝阵烧蚀对于丝阵Z箍缩动力学的研究至关重要。采用简单模型数值模拟了烧蚀过程, 该模型物理上采用绝热、单流体、单相、磁流体力学近似, 数值上采用欧拉法结合保单调输运格式来离散。数值结果很好地展示了烧蚀过程的主要特征, 例如芯-冕结构、径向等离子体流、轴线上先驱等离子体柱的形成、静止丝芯的长寿命以及延长的烧蚀期, 一些关键时间参数定量或定性地相符于文献报道的实验和数值结果, 例如冕等离子体角向融合的时刻、等离子体首次到达轴线的时刻、丝芯静止持续的时间、最后的箍缩滞止时刻, 但某些方面略有差异。

在拉格朗日坐标系下,建立了描述Z箍缩等离子体内爆动力学过程的一维三温辐射磁流体力学方程组,并编制了相应的拉氏程序.利用该程序对美国Sandia实验室Saturn装置上的铝丝阵列内爆实验进行了数值模拟,得到了内爆等离子体各参量的时空分布.其中内爆到心时刻、X光峰值功率、X光总能量等计算结果与实验结果基本一致.表明所建立的物理模型和编制的程序是合理和可靠的.