Segregation, or demixing, of flowing mixtures of size-disperse noncohesive spherical particles is well understood. However, most particle systems in industry and geophysics involve nonspherical particles. Here, the segregation of bidisperse mixtures of millimeter-sized particles having various shapes is characterized using discrete element method simulations of gravity-driven free-surface granular heap flow. As a proxy for nonspherical particles, we study mixtures of cylindrical particles that vary widely in both their length and diameter ratios, including both disks and rods, as well as mixtures of cylindrical and spherical particles. The propensity to segregate is measured with a segregation length scale that characterizes the segregation velocity of the two species for these types of mixtures, identical to the approach for mixtures of spherical particles. Surprisingly, segregation can be predicted based solely on the volume ratio of the two species, regardless of particle shape. The segregation length scale increases linearly with the log of the volume ratio for volume ratios varying from 0.1 to 10 in the same way as it does for bidisperse mixtures of spherical particles. Thus, segregation properties based on spherical particles can be directly applied to nonspherical particles.

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预测非球形颗粒的偏析

大小分散的非粘性球形颗粒的流动混合物的分离或混合是众所周知的。但是，工业和地球物理学中的大多数粒子系统都包含非球形粒子。在此，使用重力驱动的自由表面颗粒堆流的离散元素方法模拟来表征具有各种形状的毫米大小的颗粒的双分散混合物的分离。作为非球形颗粒的替代物，我们研究了长度和直径比变化很大的圆柱形颗粒混合物，包括圆盘和棒，以及圆柱形和球形颗粒的混合物。偏析的倾向用偏析长度尺度来衡量，该尺度表征了这两种混合物对两种物质的偏析速度，与球形颗粒混合方法相同。令人惊讶地，可以仅基于两种物质的体积比来预测分离，而与颗粒形状无关。对于体积比，从0.1到10，偏析长度尺度随体积比的对数线性增加，与球形颗粒的双分散混合物相同。因此，基于球形颗粒的偏析性质可以直接应用于非球形颗粒。