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Unsteady flow, clusters, and bands in a model shear-thickening fluid.
Physical Review E ( IF 2.2 ) Pub Date : 2020-01-01 , DOI: 10.1103/physreve.101.012602
Shibu Saw 1 , Matthias Grob 1 , Annette Zippelius 1 , Claus Heussinger 1
Affiliation  

We analyze the flow curves of a two-dimensional assembly of granular particles which are interacting via frictional contact forces. For packing fractions slightly below jamming, the fluid undergoes a large scale instability, implying a range of stress and strain rates where no stationary flow can exist. Whereas small systems were shown previously to exhibit hysteretic jumps between the low and high stress branches, large systems exhibit continuous shear thickening arising from averaging unsteady, spatially heterogeneous flows. The observed large scale patterns as well as their dynamics are found to depend on strain rate: At the lower end of the unstable region, force chains merge to form giant bands that span the system in the compressional direction and propagate in the dilational direction. At the upper end, we observe large scale clusters which extend along the dilational direction and propagate along the compressional direction. Both patterns, bands and clusters, come in with infinite correlation length similar to the sudden onset of system-spanning plugs in impact experiments.

中文翻译:

模型剪切增稠流体中的非定常流动,簇和带。

我们分析了通过摩擦接触力相互作用的二维颗粒颗粒组装的流动曲线。对于稍低于堵塞的填料,流体会发生大规模的不稳定性,这意味着在一定的应力和应变率范围内,不存在固定流动。以前显示的小型系统在低应力分支和高应力分支之间表现出滞后跃迁,而大型系统则表现出连续的剪切增厚,这是由于平均不稳定的空间异质流而产生的。发现观察到的大规模模式及其动力学取决于应变率:在不稳定区域的下端,力链合并形成沿压缩方向跨越系统并沿膨胀方向传播的巨型带。在高端,我们观察到沿着膨胀方向延伸并沿压缩方向传播的大型星团。模式,带和簇都具有无限的相关长度,类似于冲击实验中系统跨度塞突然出现。
更新日期:2020-01-14
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