In this paper it is shown that the gas #ow pattern in the dense bottom-bed of circulating #uidized beds, operated with Geldart-B type of solids, exhibits three di!erent types of dynamic behavior, dependent on the width of the riser and on the aspect ratio of the dense bottom-bed. These types of dynamic behavior are de"ned as: (a) &exploding bubble with wall e+ect' in risers with a diameter smaller than 0.7 m and with a bed aspect ratio smaller than 3.5; (b) &exploding bubble without wall e+ect' in risers with a diameter larger than 0.7 m and with a bed aspect ratio smaller than 3.5; (c) &circulating slugging' in narrow risers at bed aspect ratios larger than 5. The term &wall e!ect' indicates that the wall of the riser imposes limitations to the growth of the exploding bubbles and to the solids #ow in the dense bottom-bed. Non-dimensional correlations are presented, for each of these types of dynamic behavior, for the Kolmogorov entropy, quantifying the dynamic #ow behavior, and for the decay-parameter a, describing the decay of the solids volume fraction in the splash zone above the bottom-bed. These correlations were developed using pressure #uctuation and time-averaged pressure-drop data that were measured in "ve CFB risers varying in size from 0.083 m ID to 1.2;0.8 m using the same type of Geldart-B sand.