自由面被烧蚀磁驱动飞片的数值模拟

Numerical simulation of magnetically driven flyer plate of ablated free surface

为了理解磁驱动飞片自由面烧蚀的机理、自由面被烧蚀后飞片的物质状态、自由面被烧蚀后激光速度干涉仪(VISAR)测量的机理等,采用磁驱动数值模拟程序MDSC2对聚龙一号装置上PTS-151发次磁驱动飞片实验中370μm厚飞片进行了模拟和分析。数值模拟表明,334ns之前飞片自由面部分保持固体状态,334ns之后飞片自由面部分已经熔化,到340ns后整个飞片都被熔化。飞片自由面烧蚀的主要机制是电流焦耳加热,热扩散和压缩做功的贡献很小。数值模拟的固体密度反射面速度历史和VISAR测量的速度历史一致。飞片自由面熔化后,VISAR测量的速度是距离自由面最近的固体密度反射面的速度。

Magnetically driven flyer plate experiments, shot 151 with 370 μm thick aluminum flyer plate, carried out in the large current pulse device PTS are simulated and anlayzed with the two-dimensional magneto-hydrodynamics code MDSC2. Nu- merical simulation shows that the material of the whole flyer plate melts or evaporates due to ablation. Density of the material near the free surface and the loading surface of the flyer plate is low, however, that of the remaining part between the free surface and the loading surface is high. This finding tells us that the velocity measured by VISAR in the experiments may not be the ve- locity of the liquid-solid interface but be the velocity of the solid density reflecting interface, since the laser of the VISAR will pen- etrate through the free surface part whose density is lower than that of the solid density reflecting interface and reflect back at the solid density reflecting interface. This idea is confirmed by the coincidence of the simulated velocity of the solid density reflecting interface and the velocity measured by the VISAR.