研究人员通过数值实验，来研究干湿流动中颗粒形状对颗粒偏析的影响。为了分离前者，研究人员将干燥、双分散的球体混合物与旋转滚筒中的球体和立方体混合物进行了比较。结果表明，虽然偏析程度通常随着粒径比的增大而增加，与只有球体的情况相比，立方体的存在使偏析程度降低。此外，研究发现，偏析程度的差异取决于构成每个尺寸类别的形状，反映了较小颗粒为立方或球形时流动性的差异。
研究在模拟剪切驱动的耦合流体—颗粒流(例如，模拟河床)时，发现了类似的动力学现象，表明这种现象并非旋转滚筒所独有。然而，与干燥体系相反，研究发现立方颗粒存在时，偏析程度增加，流体阻力效应可以定性地改变偏析趋势。结果证明了干湿流动中相互竞争的形状诱导的分离模式，这些模式独立于粒度控制，对许多工业和地球物理过程具有启示意义。
据了解，工业和环境颗粒流通常表现出一种被称为“颗粒分离”的现象，在这种现象中，颗粒根据物理特征(大小、形状、密度)分离，干扰工业应用(水泥搅拌、药物和食品生产)，并从根本上改变地球物理流动(山体滑坡、泥石流、火山碎屑流、河床)的行为。虽然尺寸引起的偏析已经得到了很好的研究，但颗粒形状的作用还没有得到很好的研究。
附：英文原文
Title: How particle shape affects granular segregation in industrial and geophysical flows
Author: Cúez, Fernando David, Patel, Div, Glade, Rachel C.
Issue&Volume: 2024-1-29
Abstract: Industrial and environmental granular flows commonly exhibit a phenomenon known as “granular segregation,” in which grains separate according to physical characteristics (size, shape, density), interfering with industrial applications (cement mixing, medicine, and food production) and fundamentally altering the behavior of geophysical flows (landslides, debris flows, pyroclastic flows, riverbeds). While size-induced segregation has been well studied, the role of grain shape has not. Here we conduct numerical experiments to investigate how grain shape affects granular segregation in dry and wet flows. To isolate the former, we compare dry, bidisperse mixtures of spheres alone with mixtures of spheres and cubes in a rotating drum. Results show that while segregation level generally increases with particle size ratio, the presence of cubes decreases segregation levels compared to cases with only spheres. Further, we find differences in the segregation level depending on which shape makes up each size class, reflecting differences in mobility when smaller grains are cubic or spherical. We find similar dynamics in simulations of a shear-driven coupled fluid-granular flow (e.g., a simulated riverbed), demonstrating that this phenomenon is not unique to rotating drums; however, in contrast to the dry system, we find that the segregation level increases in the presence of cubic grains, and fluid drag effects can qualitatively change segregation trends. Our findings demonstrate competing shape-induced segregation patterns in wet and dry flows that are independent from grain size controls, with implications for many industrial and geophysical processes.
DOI: 10.1073/pnas.2307061121
Source: https://www.pnas.org/doi/abs/10.1073/pnas.2307061121