A simulation model of a dry, vibrated, fluidized medium (VFM) with sinkhole arrangement was developed and used to investigate the separation of relatively dense, coarse particles. The objective of the new model was to emulate a most unusual experimental result involving the sinkhole arrangement, separation densities much higher than the bulk density of the fluidized medium. The VFM was simulated using spherical sand particles 225μm in diameter, and density of 2500 kg/m3, while spherical coarse particles 2 to 4 mm in diameter, with density ranging from 2100 to 8400 kg/m3, were used as the density tracers. Coupled computational fluid dynamics (CFD)/discrete element method (DEM) was used to simulate interactions for up to 10 s duration. Remarkably, the model reproduced separation densities much higher than the bulk density of the suspension. Different combinations of frequency and amplitude of vibration, air flow velocity, and volume of VFM were used. The separation density was found to scale directly with the amplitude, and scale with the frequency to the 0.33 power. Vibration intensity correlated poorly with separation density. The critical condition governing the tendency of a particle to float or sink was examined in terms of the volume fraction and the density of the bed profile in the vicinity of the sinkhole. A pronounced reduction in the bed density is evident near the base of the VFM for particles that sink. The average solid volume fraction is observed to vary from 0.58 during initial settling, decreasing as the particles sink. Interestingly, re-circulation of the VFM is needed for a tracer particle to sink. Re-circulation is dependent on, and increases with, airflow as the bed expands up to a maximum beyond which it again reduces.

中文翻译：

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基于密度分离粗颗粒的干式振动流化天坑系统模型研究


开发了具有天坑布置的干燥、振动、流化介质 （VFM） 的模拟模型，并用于研究相对密集、粗颗粒的分离。新模型的目标是模拟一个最不寻常的实验结果，涉及天坑布置，分离密度远高于流化介质的堆积密度。VFM 使用直径为 225 μm、密度为 2500 kg/m3 的球形砂粒进行模拟，而直径为 2 至 4 mm、密度范围为 2100 至 8400 kg/m3 的球形粗颗粒用作密度示踪剂。耦合计算流体动力学 （CFD）/离散元法 （DEM） 用于模拟长达 10 s 持续时间的相互作用。值得注意的是，该模型再现的分离密度远高于悬浮液的堆积密度。使用了振动的频率和幅度、气流速度和 VFM 体积的不同组合。发现分离密度直接与振幅成比例，并随频率成比例，达到 0.33 次方。振动强度与分离密度的相关性差。根据天坑附近床层剖面的体积分数和密度来检查控制颗粒漂浮或下沉趋势的临界条件。对于下沉的颗粒，在 VFM 底部附近，床层密度的明显降低是明显的。观察到平均固体体积分数在初始沉降期间从 0.58 开始变化，随着颗粒下沉而降低。有趣的是，示踪粒子需要 VFM 的再循环才能下沉。再循环取决于气流，并随着气流的增加而增加，因为床层会膨胀到最大值，超过该最大值后，它会再次减少。