Abstract The shock dispersal of particle shells or rings by radially divergent impulsive loads takes the form of coherent particle jets which have much larger dimensions from those associated with the constituent grains. In the present study, quasi-two-dimensional particle jetting is studied via both experiments based on a radial Hele-Shaw cell and numerical simulations using the discrete element method. Simulations agree well with the experiments in terms of the branched jet pattern and characteristic timescale for jet growth. Besides simulations reproduce the signature events defining the jet formation observed in experiments, specifically the initiation of incipient jets from the non-perturbed internal surface of ring, as well as the concurrent ramification and annihilation of jets. More importantly the particle-scale simulations reveal the physics underlying the jet inception. We found that the onset of particle jetting corresponds to the transition of the shock jammed band which homogeneously expands outwards to the unevenly spaced localized shear flows, or equivalently, unjamming of the dynamic jamming front.

中文翻译：

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冲击诱导粒子喷射的开始

摘要 粒子壳或环在径向发散的脉冲载荷下的冲击扩散采用相干粒子射流的形式，其尺寸比与组成颗粒相关的粒子射流大得多。在本研究中，准二维粒子喷射通过基于径向 Hele-Shaw 单元的实验和使用离散元方法的数值模拟进行研究。在分支射流模式和射流增长的特征时间尺度方面，模拟与实验非常吻合。除了模拟再现定义在实验中观察到的射流形​​成的特征事件，特别是从环的非扰动内表面开始初始射流，以及射流的并发分支和湮灭。更重要的是，粒子尺度模拟揭示了喷流起源背后的物理原理。我们发现粒子喷射的开始对应于激波阻塞带的过渡，它均匀地向外扩展到不均匀间隔的局部剪切流，或者等效地，动态阻塞前沿的解除阻塞。