Questions about the initial fluidization velocity test for multi-rotor baffle fluidized bed reactors?

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To determine the initial fluidization velocity of a multi-rotating baffle fluidized bed reactor, a catalyst layer 16 cm high was filled in a glass tube with an inner diameter of 30 mm. The volume of gas at the point when the catalyst layer began to expand and the particles started to move was measured; the gas flow rate calculated from this value represented the initial fluidization velocity. When the catalyst layer height was increased to 32 cm, which is twice the height used in the previous experiment, the measured initial fluidization velocity differed significantly from that obtained in the previous test. Since the formula for calculating the initial fluidization velocity does not include any term related to mass, it can be inferred that the initial fluidization velocity is independent of the mass of the catalyst loaded. Based on this conclusion, the results of the two experiments should be identical, but there was a clear difference between them in practice. Any expert with experience in operating or designing fluidized beds could please provide a theoretical explanation. Thank you! Another hypothetical experiment: A catalyst 16 cm high is filled into a glass tube with an inner diameter of 30 mm, and another catalyst 16 cm high is filled into a glass tube with an inner diameter of 60 mm. Since the inner diameter of the glass tube in the latter experiment is twice that of the former, the amount of catalyst used is also twice as much. Will the initial fluidization velocities for these two sets of experiments be the same? (Since there is no glass tube with an exact inner diameter of 60 mm available in the laboratory, this verification experiment was not carried out.) Should it be the same according to the formula for calculating the initial fluidization velocity?) The catalyst used in the experiment was the same, and the fluidizing gas was air.