Characterization of Intermittent Solids Flow

As noted, a high degree of voidage fluctuation is associated with the bursting of wavy solids layer into clusters. The intermittency of the bursting and the cluster velocity are elaborated in the following. 

The intermittent nature of the local solids flow behavior in a riser can be quantified on the basis of the intermittency index defined as [Brereton and Grace, 1993a] 

The general trend of the intermittency index obtained experimentally for, as an example, U = 6.5 m/s and Jv = 42 kg/m2 s (case (a)) and 62 kg/m2 s (case (b)), is given in Fig. 10.17. The results indicate that the intermittency index varies between 0.1 to 0.7. These values imply that the gas-solid flow in the riser is never solely in the ideal 

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