Swirl motions of a bubbling jet in a cylindrical bath with bottom gas injection through a centric single-hole nozzle were investigated. The swirl motions were classified into two kinds. One was observed when the bath depth HL, was less than about the bath diameter D, while the other occurred for HL/D_??_2. These two kinds of swirl motions were named the first and the second kind, respectively. For the first kind swirl motion, conditions giving the onset and cessation of it were clarified. An empirical correlation for the cessation of the swirl motion was proposed. The swirl cycle was found to be closely related to the cycle of sloshing. On the other hand, the second kind swirl motion was considered to be caused by an instability of a large scale ring vortex enclosing the bubbling jet. Empirical correlations for the onset of swirl motion and the swirl cycle were derived.
