Discussion: “Measured Passage Velocities in a Radial Impeller With Shrouded and Unshrouded Configurations” (Howard, J. H. G., and Kittmer, C. W., 1975, ASME J. Eng. Power, 97, pp. 207–212)

showed the strong influence of the flow entering the passage due to the clearance between the blade tips and the stationary shroud. The strongest vorticity was near the tip but it spread into the midpassage toward the impeller side. A large single vortex was established which filled the passage. Viscous effects on the hub surface accounted for the vorticity in the opposite direction close to the hub. Despite the considerable change in the secondary flow pattern between the shrouded and unshrouded versions, it appears that the average primary velocity profile was basically unaltered. However, some disturbances in the unshrouded impeller can be noted near the blade tip in Figs. 9 to 12, which lead, at the passage exit, to decreasing radial velocities and increasing slip angles toward the tip.