Abstract An experimental study of the flow regimes and transitions in a fluidized bed (cross-section of 200 mm × 200 mm and height of 2000 mm) containing a mixture of cylindrical particles and silica sand is carried out. Six different flow regimes are identified: fixed bed (F), bubbling fluidization (B), transition fluidization (T), partial fluidization (P), complete fluidization (C) and unable to fluidize (N). The flow regime characteristics are described using schematic diagrams and photographic images. Based on the flow regime classification, three types of flow regime transition routes are explained. The effect of various operating parameters on the flow regime transition is determined and the resulting flow regime map is presented. Two unstable fluidization patterns are observed and their fluidization mechanisms are discussed. It is shown that the change of the Δ P - u f profile, where Δ P is the bed pressure drop and u f is the superficial gas velocity, indicates when a flow regime transition occurs and the reproducibility of the Δ P - u f curve identifies fluidization stability. Furthermore, a contact force model for a cylindrical particle in a bed material cloud is developed considering particle orientation, based on which a theoretic model for cylindrical particle fluidization termination velocity ( u b ) was derived and validated.