The sparger with diamete of 0.08 m and 16 holes (diameter of 0.0015 m) is
installed underneath the impeller. The off-bottom clearance of the
sparger is T/10 in most experiments; and T/4 and T/6 are just used
to test the influence of sparger locations with respect to the
impeller. Different types of stirrers are used as shown in Fig. 2,
namely, Rushton disk turbine (RDT), half circle blade disk turbine
(HCDT), 451 pitched blade turbine downflow (PBTD) and 451
pitched blade turbine upflow (PBTU). The four impellers have