An unsteady potential flow model of bubble-induced particle motion near a horizontal tube in a fluidized bed

An unsteady hydrodynamic model of bubble-induced particle motion near a horizontal tube immersed in a gas-fluidized bed is proposed. According to the model, a two-dimensional bubble rising past the tube is treated as a moving doublet so that particle motion relative to the bubble is analogous to the potential flow of a gas past a circular cylinder. Also, the condition that particles should not penetrate the tube wall is established using the method of images. The particle velocities induced by the rising bubble are used together with a numerical integration scheme to establish particle trajectories near the tube wall. Results of calculations are shown to compare qualitatively with experimental observations by others. Further calculations illustrate the effect of bubble size upon particle motion in the defluidized cap on the leeward side of the tube.

The proposed model could be used as a basis for estimation of emulsion phase residence time or improved interstitial gas velocity estimates required for heat transfer analyses.