Nonadditive drag of tandem rods drafting in granular sediments
Nonadditive drag of tandem rods drafting in granular sediments
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颗粒沉积物中串联杆牵伸的非加性阻力
DOI：
10.1103/physreve.105.034901
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发表时间：
2022
影响因子：
2.4
通讯作者：
Kudrolli, Arshad
中科院分区：
文献类型：
--
作者：
Chang, Brian;Kudrolli, Arshad
我们研究了一对垂直杆在浸泡在流体中的颗粒床中串联移动时所经历的阻力，这是它们分离距离和速度的函数。就像在牛顿流体中一样，杆子最初感受到的净阻力随着距离单根杆子达到平台值的两倍而增加。然而，作用在两根杆子上的阻力是非常不同的，与单独的杆子相比，前面的杆子承受的阻力大致相同，而后面的杆子承受的阻力要小得多。无论是在干燥的颗粒床中，还是在粘性牛顿流体中，在准静态区域和速率相关区域，都可以观察到阻力与前后物体之间的距离的反常关系。通过折射率匹配，我们可视化了通过两个杆的泥沙流动，并表明在两个杆之间的参考系中，对于小的分离，会形成一个停滞区。因此，随着分离距离的减小，跟随杆越来越不受颗粒流的影响，从而导致较低的净阻力。在将阻力理论应用于颗粒沉积物中运动的多组分物体时应谨慎，因为我们的结果是，在较短的间隔距离内，阻力不是相加的。
We examine the drag experienced by a pair of vertical rods moving in tandem through a granular bed immersed in a fluid as a function of their separation distance and speed. As in Newtonian fluids, the net drag experienced by the rods initially increases with distance from the value for a single rod before plateauing to twice the value. However, the drag acting on the two rods is remarkably different, with the leading rod experiencing roughly similar drag compared to a solitary rod, while the following rod experiences far less drag. The anomalous relationship of drag and the distance between the leading and following body is observed in both dry granular beds and while immersed in viscous Newtonian fluids across the quasistatic and the rate-dependent regimes. Through refractive index matching, we visualize the sediment flow past the two rods and show that a stagnant region develops in their reference frame between the rods for small separations. Thus, the following rod is increasingly shielded from the granular flow with decreasing separation distance, leading to a lower net drag. Care should be exercised in applying resistive force theory to multicomponent objects moving in granular sediments based on our result that drag is not additive at short separation distances.