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Fluidized beds have applications in a range of industrial sectors from oil refining and coal combustion to pharmaceutical manufacture and ore roasting. In spite of more than 80 years of industrial experience and a tremendous amount of academic attention, the fundamental understanding of fluidized bed hydrodynamics is still far from complete. Advanced modeling using computational fluid dynamics is one tool for improving this understanding. In the current chapter the focus is on the application of CFD to a particularly challenging yet industrially relevant area of fluidization: fluidized beds containing Geldart A powders where interparticle forces influence the bed behavior. A critical step in modeling these systems is proper representation of the interfacial drag closure relations. This is because the interparticle cohesive forces lead to the formation of clusters that reduce the drag below that for non-cohesive particles. The influence on the predictions of the macroscale fluidized behavior due to mesoscale phenomena such as clustering is discussed. At present in the literature, approaches to representing the reduced drag arising from mesoscale phenomena is ad hoc. There is a pressing need for an improved understanding of cluster formation and for robust models describing it that can be incorporated into coarse grid models of industrial scale fluidized beds.