The complex dynamics of a circulating fluidized bed with a 0.205 m i.d. riser has been characterized by chaotic time series analysis of local voidage and pressure flucturations. At low solid holdup the voidage fluctuation was found to exhibit a high dimensional attractor reflected by local small-scale turbulence in beds. With increasing local solid holdup the particle particle collision becomes more significant, reducing both te correlation dimension and Kolmogoroventropy due to the suppression of chaotic motion of individual particles and cluster formation. On the other hand, the pressure fluctuation is governed by the global hydrodynamics with a relatively low attractor dimension.
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