The particle velocity field inside a bubbling fluidized bed exhibits strong unsteady flow patterns accompanied by intense meso-scale fluctuations induced by the motion of bubbles: state-of-the-art post-processing methodology, namely the proper orthogonal decomposition (POD), is applied to the fluctuating particle flow fields predicted by a two-fluid model of a bubbling bed to identify and analyze the dominant spatio-temporal patterns of the particle phase. Three-dimensional POD results indicate that the dominant particle fluctuating velocity patterns are principally aligned in the axial direction, corresponding to particle mixing by the bubble wakes, with significant laterally-directed fluctuating velocity vectors at the bed surface, corresponding to mixing caused by the bubbles bursting. The swirling strength criterion is also used to identify particle vortical motions.
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