Experimental study of the transition between unsteady flow regimes in a partially aerated two-dimensional bubble column

The experiments performed in this article led to the identification of the characteristic flow patterns generated in a rectangular bubble column when a partially aerated plate is used. Considering the traditional time-averaged approach and based on the flow regimes identified by several authors, it is concluded that the flow regime existing at all values of the superficial gas velocity (UG from 1.2 mm/s to 21.3 mm/s) is the coalesced bubble regime. Furthermore, homogeneous and turbulent regimes are not observed and the prevailing flow regime is the 3-region vortical regime. However, focusing on both the local and instantaneous values of the most characteristic flow variables, it is possible to identify different flow regimes from those previously described as a function of UG. Based on this approach, it is proposed for the first time the existence of three new flow patterns included in the generic vortical flow regime: the dispersed bubble vortical flow (DBVF), the transition vortical flow (TVF) and the fully developed vortical flow (FDVF). The main characteristics of these new flow regimes and the hydrodynamic variables that determine the transition between them are presented.