Bubble behavior in cylindrical and square vessels under centric mechanical stirring

Water model experiments were carried out to investigate the bubble behavior in cylindrical and square vessels under centric mechanical stirring. The bubble behavior in the square vessel was investigated in detail by using a high-speed camera to record the transient images of the bubbles. An image analysis software was used to obtain the bubble diameter. The results showed that the centric mechanical stirring in the square vessel was suitable for breakage and dispersion of bubbles, but not suitable for that in the cylindrical vessel. Increasing the impeller blade length and impeller rotation speed was beneficial to disintegrate and disperse bubbles widely. The bubble diameter decreased with the increase in the Weber number and increased slightly with the increase in the modified Froude number. The dimensionless correlation equation of bubble diameter was obtained by the dimensional analysis method.