QUANTITATIVE-ANALYSIS AND COMPUTATION OF 2-DIMENSIONAL BUBBLE-COLUMNS

Experiments conducted quantify the macroscopic hydrodynamic characteri stics of various scale 2-D bubble columns, which include dispersed and coalesced bubble regimes characterized by two flow conditions (4- and 3-region flow) with coherent flow structures. Hydrodynamic behavior i s analyzed based on flow visualization and a particle image velocimeti y (PIV) system. Columns operated in the 4-region flow condition compri se descending vortical, fast bubble and central plume regions. The fas t bubble flow region moves in a wavelike manner, and thus the flow in the vicinity of this region is characterized macroscopically in terms of wave properties. In columns greater than 20 cm in width, the transi tion from the dispersed bubble flow regime to the 4- and then to 3-reg ion flow in the coalesced bubble regime occurs progressively with gas velocities at 1 and 3 cm/s, respectively. The demarcation of flow regi mes is directly related to measurable coherent flow structures. The in stantaneous and time-averaged liquid velocity and holdup profiles prov ided by the PIV system are presented in light of the macroscopic flow structure in various 2-D bubble columns. Numerical simulations demonst rate that the volume of fluid method can provide the time-dependent be havior of dispersed bubbling flows and account for the coupling effect s of pressure field and the liquid velocity on the bubble motion. Comp arison of computational results with PN results for two different bubb le injector arrangements is satisfactory.