冲击波作用下微米尺度金属颗粒群的动力学行为

Dynamical behaviors of Sn micro-sphere particles under shock wave action

基于平面化爆驱动飞片高压加载技术和激光测速技术,研究了冲击波加载不同粒径锡颗粒群的微喷射行为以及在空气中的减速规律.实验结果表明,锡颗粒的最快喷射速度随粒径增大而显著增大.通过对微喷射形成过程的三维光滑粒子流体动力学方法数值模拟发现,大粒径锡颗粒之间存在较大的空隙结构,冲击波与空隙结构的相互作用诱导产生高速汇聚射流,空隙结构越大对应的喷射速度也越高.此外,通过研究不同粒径颗粒在复杂流场中的减速规律,进一步深化了对微喷射破碎后的颗粒尺度状态以及混合输运特性的认识.研究结果对于预测和分析冲击波加载微米颗粒群的微喷混合特性具有一定价值.

In these decades, the turbulence mixing of micro-ejecta particles and gas has attracted considerable attention because it has great influence on inertial confinement fusion and some technologies of optical detection. It is significantly important for studying the evolution of micro-ejecta by investigating the influence of particle size and the transporting progress. In this paper, we experimentally investigate the micro-ejecta dynamical behaviors when a strong shockwave acts on Sn micro-sphere particles with different sizes of 0.1 μm, 1 μm, 5 μm and 10 μm. A strict experiment is carried out, in which a thin Ta flyer is accelerated by TNT explosion to load the Sn particles, and the velocity variation of ejecta particles transported in air is measured by the displacement interferometer system for any reflector. The results show that the tip-velocity of the micro-ejecta is very sensitive to the initial size of particle, where the larger size results in increased velocity. By analyzing the results of each case in detail, we discover that the formation of micro-ejecta is caused by the interaction between shockwave and the gap structure among several particles, where the larger gap structure induces faster ejecta tip-velocity. To verify this explanation, the effects of particle size on the ejecta tip-velocity is examined by simulating the cases of 5 μm and 10 μm in particle size through three-dimensional smooth particle hydrodynamics method. The simulated tip-velocity results are in good agreement with the corresponding experimental results. However, the scenario is different when the particle size is smaller than 1 μm, where the experimentally measured tip-velocity of 0.1 μm size particle is nearly the same as that of 1 μm size particle. We attribute this to the fact that the gap structure is too small to affect the micro-ejecta progress and the micro-ejecta is mainly caused by the large scale defects accumulated by a huge number of particles. Furthermore, by comparing with the experimentally measured velocity decay, we also estimate the size distribution of ejecta particles by simulating the decelerating processes of different-sized particles with different initial velocities in gas. This paper is helpful in comprehending in depth the micro-ejecta process caused by the shockwave acting on micro particles, and also in designing such experiments accurately.