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Morphodynamics of a dense particulate medium under radial explosion.
Soft Matter ( IF 2.9 ) Pub Date : 2020-01-13 , DOI: 10.1039/c9sm02150g
Kun Xue 1 , Panpan Han , Kaiyuan Du , Yixiang Gan , Ziwei Wang , Chunhua Bai
Affiliation  

In this paper, we investigate the initiation and growth of instability patterns arising from the shock loaded internal surfaces of granular rings confined in a Hele-Shaw cell using both experimental and numerical approaches. A variety of patterns are formed in granular media consisting of grains with varying morphologies. When the particle shape becomes increasingly irregular, and/or the gap in the Hele-Shaw cell becomes narrower, it is increasingly hard for confined particles to fluidize. Consequently the emergent pattern transitions from a smooth circle with trivial undulation which grows in a self-similar manner to an unstable finger-like structure with significant tip-splitting. The distinct growth mode of the well-defined instability pattern is closely associated with its inception phase alongside the transmission of the compaction front. The runaway growth of the incipient perturbations gives rise to the unstable growth of the late-time finger-like instabilities. Conversely the minimal growth of the perturbations in the inception phase guarantees the ensuing self-similar growth of the instability patterns featuring insignificant corrugation. The grain-scale simulations reveal the fundamental role played by the heterogeneous non-linear force network inherent to granular media in the stable-to-unstable transition of the instability pattern. The present work reveals the correlation between the grain-scale physics underpinning the formation of surface instability upon shock loading granular media and the nature of the resulting macro-scale instability patterns. The macroscopic flowability of particles through the confined space is found to be the foremost indicator of the nature of the shock induced granular instability pattern.

中文翻译:

径向爆炸下稠密颗粒介质的形态动力学。

在本文中,我们使用实验和数值方法研究了由Hele-Shaw单元中的颗粒环内表面的冲击载荷内表面引起的不稳定性模式的萌生和增长。在由具有不同形态的晶粒组成的颗粒状介质中形成了各种图案。当颗粒形状变得越来越不规则,和/或Hele-Shaw池中的间隙变窄时,受限颗粒难以流化。因此,出现的模式从具有微小波动的平滑圆过渡,该平滑圆圈以自相似的方式增长为具有明显的尖端裂开的不稳定的手指状结构。明确定义的不稳定性模式的不同增长模式与它的开始阶段以及压实前沿的传递密切相关。初期扰动的失控增长导致后期手指状不稳定性的不稳定增长。相反,在初始阶段,扰动的最小增长保证了随之而来的以微不足道的波纹为特征的不稳定性模式的自相似增长。晶粒度模拟揭示了颗粒介质固有的异质非线性力网络在不稳定模式的稳定到不稳定过渡中所起的基本作用。本工作揭示了在冲击加载颗粒状介质时支撑表面不稳定性形成的晶粒尺度物理学与所产生的宏观尺度不稳定性模式的性质之间的相关性。
更新日期:2020-02-13
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