The effect of the number and placement of feed points was simulated in various vessels described in the literature by extending a previously published and validated axisymmetric 2D compartment model to include more compartments and the tangential dimension. Additional compartments were necessary for accurate feed point placement, and the model extension followed previously published networks-of-zones models . Briefly, the main circulation and exchange flows as defined in references , C = C 3 and E = E 3 (L 3 T -1 ), were calculated as a function of stirrer speed (T -1 ) and impeller diameter (L) with dimensionless circulation and exchange flow numbers, C and E .