We investigate experimentally the nonequilibrium features in a pseudo 2‐D bubbling fluidized bed. Velocities of individual particles are measured by using a particle tracking velocimetry (PTV) method, and void fractions are obtained with the Voronoi tessellation. A bimodal shape of probability density function (PDF) for particle vertical velocity is found in not only time‐averaged but also time‐varying statistics, which is caused by the transition between the dense and dilute phases and breaks the local‐equilibrium assumption in continuum modeling of fluidized beds. The results of time‐varying radial distribution function and voidage distribution also confirm this finding. Moreover, the analysis of voidage, particle velocity, granular temperature and turbulent kinetic energy of particles shows that there is no scale‐independent plateau over the interface, and it seems hard to find a scale‐independent plateau to separate the micro‐ and meso‐scales of fluidized beds, which require sub‐grid meso‐scale modeling for continuum or coarse‐graining methods of gas‐fluidized systems. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2364–2378, 2018

中文翻译：

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鼓泡流化床中与尺度有关的非平衡特征

我们通过实验研究了伪二维鼓泡流化床中的非平衡特征。通过使用粒子跟踪测速（PTV）方法测量单个粒子的速度，并使用Voronoi镶嵌技术获得空隙率。不仅在时间平均而且在时变统计中都发现了粒子垂直速度的概率密度函数（PDF）的双峰形状，这是由稠密相和稀相之间的过渡引起的，并打破了连续体中的局部平衡假设流化床建模。随时间变化的径向分布函数和空隙率分布的结果也证实了这一发现。此外，空隙率，粒子速度，颗粒的颗粒温度和湍动能表明界面上没有尺度无关的平台，并且似乎很难找到尺度无关的平台来分离流化床的微观和中尺度，这需要亚网格气体流化系统的连续或粗粒度方法的中尺度建模。©2018美国化学工程师学会AIChE J，64：2364–2378，2018