窄缝固液流化床中粘结颗粒的运动与聚团
Motion and clustering of bonded particles in narrow solid-liquid fluidized beds
摘要：
本文介绍了固-液流化床的实验和数值研究的粘结球在很窄的管，即，当管直径和颗粒直径之间的比率较小时。在窄床中，高限制效应已被证明会导致结晶、堵塞和不同的图案，如果一些颗粒结合在一起，这些图案可以被强化或修改。为了研究这一点，我们生产了直径为4.8 mm的粘合铝球的二组和三组，并在25.4 mm-ID管中形成由150-300组或100-200组组成的床，其经受高于流化所需的水速度。在实验中，我们用高速和传统相机拍摄了床层，并处理了图像，获得了床层和谷物尺度的测量结果。对于数值计算部分，我们计算了相同条件下的CFD-DEM（计算流体动力学-离散元法）代码的床演变。我们的研究结果表明，不同的运动为个人二重奏和三重奏，和不同的结构内的床。我们还发现，堵塞可能会突然发生三，甚至微观运动（波动在晶粒尺度）停止，质疑这些情况下的流化条件。
英文摘要：
This paper presents an experimental and numerical investigation of solid-liquid fluidized beds consisting of bonded spheres in very narrow tubes, i.e., when the ratio between the tube and grain diameters is small. In narrow beds, high confinement effects have proved to induce crystallization, jamming and different patterns, which can be intensified or modified if some grains are bonded together. In order to investigate that, we produced duos and trios of bonded aluminum spheres with diameter of 4.8 mm, and formed beds consisting either of 150-300 duos or 100-200 trios in a 25.4 mm-ID pipe, which were submitted to water velocities above those necessary for fluidization. For the experiments, we filmed the bed with high-speed and conventional cameras and processed the images, obtaining measurements at both the bed and grain scales. For the numerical part, we computed the bed evolution for the same conditions with a CFD-DEM (computational fluid dynamics - discrete element method) code. Our results show distinct motions for individual duos and trios, and different structures within the bed. We also found that jamming may occur suddenly for trios, where even the microscopic motion (fluctuation at the grain scale) stops, calling into question the fluidization conditions for those cases.
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