Fluidization drift velocity

Parmentier J-F, Simonin O, Delsart O A functional subgrid drift velocity model for filtered drag prediction in dense fluidized bed, AICHE J 58 1084—1098, 2012. 

Darton and Harrison (1975) derived a criterion for the point of transition to predict whether a solid-liquid fluidized bed will expand or contract when the gas is first introduced. The definition of Pa used by Darton and Harrison was the ratio of upper clear (particle-free) wake volume to the bubble volume. But since they did not consider the circulation of sohds associated with the lower nonclear portion of the wake, their Pa was effectively the same as that of Bhatia and Epstein (1974). The use of the Wallis drift flux approach by Darton and Harrison (1975) also represents no real difference from the relative velocity approach taken by Bhatia and Epstein (1974), since the two methods are rigorously interrelated. It is therefore not surprising that the final criteria of Bhatia and Epstein (1974) and Darton and Harrison (1975) are identical. 

Glicksman and McAndrews (1985) determined the effect of bed width on the hydrodynamics of large particle bubbling beds. Sand particles with a mean diameter of 1 mm were fluidized by air at ambient conditions. A rectangular-cross-section bubbling bed was used. The bed width ranged from 7.6 to 122 cm, while the other cross-sectional dimension was held constant at 122 cm. Most experiments were carried out with an open bed. The bubble rise velocity increased with the bed width when the bubble velocity was represented as the drift flux plus the rise velocity of an isolated bubble,... 

Figure 13 The regime transition velocity (a) in a bubble column. Open symbols are obtained by standard deviation of pressure fluctuation and drift flux model closed symbols are calculated by the correlation of Wilkinson et al. (1992). (From Lin et al., 1999.) (b) In a three-phase fluidized bed. (From Luo et al., 1997a.)...

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