Discussion of "Mixing Time and Fluid Flow Phenomena in Liquids of Varying Kinematic Viscosities Agitated by Bottom Gas Injection"*

Mathematical modeling of the secondary current distribution in prebaked aluminum cells was used to study the influence of (1 ) a modified anode shape, (2) the curvature of the metal, and (3) an anode being set too high or too low. The calculations show that, if the lower corners of a new anode are cut off by 5 cm (diagonally), the steady-state shape of the anode is reached after 3 days, as compared to 6 to 8 days for rectangular corners. If the metal curvature corresponds to a 3 cm difference in height per 100 cm of length, and the sloping metal is facing a newly set horizontal anode, the current density varies across the anode with a maximum of 125 pet of the normal value (0.75 A cm ^-2), and it takes 4 days until the anode is aligned with the metal. If a new anode is set I cm too low or too high, the initial current through that anode after heatup is 123 and 84 pet, respectively, of the normal value, and it takes 4.2 and 7.7 days, respectively, until the interpolar distance is correct (45 ± I mm).