Nguyen Thoa T M, Sederman Andrew J, Mantle Michael D, Gladden Lynn F
Department of Chemical Engineering, University of Cambridge, Cambridge CB2 3RA, United Kingdom.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 Jul;84(1 Pt 1):011304. doi: 10.1103/PhysRevE.84.011304. Epub 2011 Jul 26.
The dynamics of granular materials, particularly radial and axial segregation in horizontal rotating cylinders containing large and small particles, is studied by Magnetic Resonance Imaging (MRI). Stationary three-dimensional (3D) images and real-time two-dimensional (2D) structural images showing radial segregation, band formation, and band merging are reported. Quantitative local particle concentrations are measured in a noninvasive manner from the different magnetic resonance responses of the seeds throughout segregation. Data are acquired with sufficiently high temporal (300 ms for 2D images) and spatial resolutions (0.94 mm cubic voxels), to give insights into the underlying mechanisms of both radial and axial segregation. In particular, the increasing rate of the local particle concentration during radial segregation is quantified. Particle migration is observed in the bulk material of the 75% and 82% full cylinders during both radial and axial segregation, showing that this region beneath the avalanche layer does not behave as a solid body. We also provide direct experimental evidence to support recent numerical simulations of band merging.
利用磁共振成像（MRI）研究了颗粒材料的动力学，特别是在包含大小颗粒的水平旋转圆柱体内的径向和轴向分离。报告了显示径向分离、条带形成和条带合并的静态三维（3D）图像和实时二维（2D）结构图像。在整个分离过程中，通过种子的不同磁共振响应以非侵入性方式测量定量的局部颗粒浓度。以足够高的时间分辨率（2D图像为300毫秒）和空间分辨率（0.94立方毫米体素）获取数据，以深入了解径向和轴向分离的潜在机制。特别是，对径向分离过程中局部颗粒浓度的增加速率进行了量化。在径向和轴向分离过程中，在75%和82%装满颗粒的圆柱体的散装材料中观察到颗粒迁移，表明雪崩层下方的该区域并非表现为固体。我们还提供了直接的实验证据来支持最近关于条带合并的数值模拟。
