A mechanism for air induced fluidization in vibrated granular beds

We present a new mechanism for the fluidization of a vibrated granular bed in the presence of interstitial air. We show that the air flow induced across the bed, as the gap in the bottom of the cell evolves, can fluidize the bed in a similar way as in gas-fluidized {\it static} beds. We use the model of Kroll to quantify the relevant variables suggested by the mechanism proposed. The relevance of the above fluidization for segregation phenomena is discussed.