In fully developed slugging fluidized beds, the maximum amplitude of absolute pressure fluctuations is reached with increasing superficial gas velocity when the slug length reaches a maximum, and the separation distance between successive slugs starts to decrease. Uc, the superficial gas velocity at which absolute pressure fluctuations reach a maximum, thus indicates the early stage of transition from slugging to core-annular flow. U,, identified based on standard deviations of differential pressure fluctuations or local voidage fluctuations, can be predicted by slug flow models and does not signify a transition to turbulent fluidization.Dans les lits fluidisCs bouchonnants pleinement dbveloppks, I'amplitude maximale des fluctuations de pression absolues est atteinte avec l'augmentation de la vitesse de gaz lorsque la longueur du bouchon atteint un maximum, et quand la distance de sbparation entre les bouchons successifs commence h diminuer. U,, la vitesse de gaz superficielle