Published online by Cambridge University Press: 20 April 2006
The gas-flow pattern that occurs when a bubble grows during its passage through a fluidized bed is investigated by applying Davidson's (1961) model in an unsteady manner. It is found that the form of the cloud perceived by an observer of this unsteady motion is significantly different from that predicted by the steady theory. Growth is shown to lead to a reduction in the penetration of the cloud ahead of the bubble and a reduction in the area of overlap between cloud and particles. The cloud boundary also interaepts the bubble boundary, and the gas entering the bubble to sustain its growth does so through its base. There is good agreement with experimental observation of clouds.