Micromechanics of intruder motion in wet granular medium
Micromechanics of intruder motion in wet granular medium
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湿颗粒介质中入侵者运动的微观力学
DOI：
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发表时间：
2018
影响因子：
2.7
通讯作者：
A. Kudrolli
中科院分区：
文献类型：
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作者：
R. Jewel;Andreea Panaitescu;A. Kudrolli
我们调查的入侵者移动通过沉积介质，其中包括透明的颗粒状水凝胶浸入水中，以及由此产生的运动的介质所遇到的有效摩擦。我们表明，有效摩擦$mu_e $上的球形入侵者被捕获的惯性数$I $给定的时间尺度上的入侵者移动和惯性时间尺度的上覆岩层压力设置的粒状介质的比率。此外，$mu_e $由函数$mu_e（I）= mu_s + alpha I ^描述eta $，其中$mu_s $为静摩擦力，$alpha $和$η 5是与材料相关的常数，其与侵入物的深度和尺寸无关。通过测量入侵者周围的颗粒组分的平均流量，我们发现入侵者和颗粒介质之间的显着滑移。与粘性牛顿流体相比，介质的运动被强烈地限制在入侵者附近，并且是入侵者大小的量级。随着介质深度的增加，介质的回流发生在离侵入物更近的地方。此外，我们研究的可逆和不可逆的位移的介质，不仅以下的介质作为入侵者向下移动，但也同时返回入侵者回到原来的深度。我们发现，流动在很大程度上保持可逆的准静态制度，以及当$mu_e $迅速增加的范围内的$I $探测。
We investigate the effective friction encountered by an intruder moving through a sedimented medium which consists of transparent granular hydrogels immersed in water, and the resulting motion of the medium. We show that the effective friction $mu_e$ on a spherical intruder is captured by the inertial number $I$ given by the ratio of the time scale over which the intruder moves and the inertial time scale of the granular medium set by the overburden pressure. Further, $mu_e$ is described by the function $mu_e(I) = mu_s + alpha I^eta$, where $mu_s$ is the static friction, and $alpha$ and $eta$ are material dependent constants which are independent of intruder depth and size. By measuring the mean flow of the granular component around the intruder, we find significant slip between the intruder and the granular medium. The motion of the medium is strongly confined near the intruder compared with a viscous Newtonian fluid and is of the order of the intruder size. The return flow of the medium occurs closer to the intruder as its depth is increased. Further, we study the reversible and irreversible displacement of the medium by not only following the medium as the intruder moves down but also while returning the intruder back up to its original depth. We find that the flow remains largely reversible in the quasi-static regime, as well as when $mu_e$ increases rapidly over the range of $I$ probed.