The much larger difference from the literature correlation may be due to the different definitions of jet penetration. Conclusions 1. In a two-dimensional fluidized bed with a circular jet there exists a maximum porosity region at a finite length above the jet inlet. This maximum increases with jet velocity. It occurs due to three-dimensional effects.2. In a two-dimensional bed with a rectangular jet of the same width as the fluidized bed, the time averaged void profiles are as they are expected to be from hydrodynamic calculations. Near the jet we have nearly elliptic profiles which then curve away from the center of the bed.3. Jet penetration depths can be determined from time-averaged porosity distributions. The actual length of jet penetration depends upon a particular definition adopted. This makes it difficult to compare the present data to various literature correlations that did not measure porosities. However, by use of the same definition, the jet penetrations for the circular and for the slit jets are very close to each other.