Multifractal characterization of flow in circulating fluidized beds

The intermittent flow in a circulating fluidized bed is shown to possess a multifractal character. The voidage signals at different solids concentrations and radial positions are characterized by defining an intermittency measure selected from a hierarchy of multifractal exponents. The intermittency profiles based on the raw measured data are consistent with the bindings of Brereton and Grace (Chem. Eng. Sci., 48 (14) (1993) 2565–2572), while the results obtained after removing the contribution from clusters match those of Jiang et al. (Circulating Fluidized Bed Technology IV, AIChE Publications, 1994, pp. 111–117). The success of multifractal characterization of CFB flow suggests that the cluster motion may behave as a multiplicative cascade process.