A new wavelet‐threshold criterion was developed to distinguish the cluster and the void phases from the transient solids holdup/concentration fluctuation signals when measured in a 108 mm‐i.d. × 5.75 m‐high circulating fluidized bed with FCC particles (d p = 78 μm, ρ p = 1,880 kg/m 3 ). An appropriate level of approximation subsignal was systematically specified as a threshold for cluster identification, based on multiresolution analysis (MRA) of wavelet transformation. By the established threshold, the dynamic properties of clusters including the appearance time fraction of clusters F cl , average cluster duration time τ cl , cluster frequency f cl , and local average solids holdup in clusters ε sc , at different radial and axial positions were determined under the turbulent, transition and fast fluidization flow regimes. The results also describe the dynamic properties of clusters and flow patterns in the splash zone along with the dense bottom region of the circulating fluidized beds.
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Yang et al. (2009) studied this question.
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