具有宽粒度分布的颗粒材料的剪切诱导混合
Shear-induced mixing of granular materials featuring broad granule size distributions
摘要：
采用离散元方法研究了剪切诱导混合过程中的颗粒流动。我们的目的是要了解的基本机制的过渡从未混合到混合相的颗粒状材料具有广泛的颗粒分布，我们系统地研究通过改变应变速率和系统的大小。在这里，应变速率变化超过四个数量级，系统尺寸从一万到一百多万个颗粒不等。从准静态到纯惯性流的应变率相关的过渡观察。在宏观尺度上，接触应力下降，由于剪切诱导的不稳定性，作为一个发病的颗粒流和启动颗粒之间的混合的形成。应力降显示出深刻的系统尺寸依赖性。在颗粒尺度上，混合动力学与剪切带的形成相关，这导致混合的时间尺度显著不同，特别是对于那些靠近系统壁和本体的区域。总的来说，我们的研究结果表明，虽然瞬态动力学显示一个通用的行为，这些有一个显着的有限尺寸效应。相比之下，宏观行为在稳定状态下，可以忽略不计的系统尺寸的依赖性。
英文摘要：
Granular flows during a shear-induced mixing process are studied using Discrete Element Methods. The aim is to understand the underlying elementary mechanisms of transition from unmixed to mixed phases for a granular material featuring a broad distribution of particles, which we investigate systematically by varying the strain rate and system size. Here the strain rate varies over four orders of magnitude and the system size varies from ten thousand to more than a million granules. A strain rate-dependent transition from quasistatic to purely inertial flow is observed. At the macroscopic scale, the contact stresses drop due to the formation of shear-induced instabilities that serves as an onset of granular flows and initiates mixing between the granules. The stress-drop displays a profound system size dependence. At the granular scale, mixing dynamics are correlated with the formation of shear bands, which result in significantly different timescales of mixing, especially for those regions that are close to the system walls and the bulk. Overall, our results reveal that although the transient dynamics display a generic behavior these have a significant finite-size effect. In contrast, macroscopic behaviors at steady states have negligible system size dependence.
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